My vmax rx7 build
Discussion
Gaz. said:
What are you going to do with the air when it leaves the radiator?
to be fair im not 100% sure, i know there is potential that ill need to do something but racing beat's rx7 is the world record holder at 242mph down bonnieville and thats not exactly the coldest of places, ive emailed them as they ran an unvented bonnet to see if they had any problems with temps
hotshot123 said:
so did you managed to keep it under budget? how does it run in ported freshly rebuilt form?
very interesting read btw!
at the moment work has slowed down because ive ran out of funds, i didnt have all the money in a bank account ready to go, so ill justy slowly be adding bits as funds come in, first thing is an ecu, then we can start with cooling.very interesting read btw!
the engine is all built and im running it in at the moment, its done 600miles up to yet, its a little lumpy and the overlap on the ports does cause a bit of misfiring if you holding the car under 2000rpm, but to make the power i want im not gonna expect perfect streetability.
Got an email back from racing beat:
Your question was forwarded to Jim Mederer, Racing Beat's co-founder and chief engineer, for review. The following is his reply to your inquiry:
Our Bonneville FD had a custom chassis with no part of the stock chassis. I made the driveline tunnel quite large to allow heated air to pass through. The entire car had a carbon fiber underpan bonded to the chassis. I used a 4" thick radiator to restrict air volume while maintaining high speed cooling. Intercooling was done with ice and water to reduce drag. I urge you to use a 4" to 5" high spoiler lip to obtain down force at the rear - critical for traction and stability.
Jim Mederer
Now he was flat out for 4miles straight so im not gonna be generating quite as much heat as he is, but its an interesting way of getting rid of heat, from what he wrote im guessing he was using a chargecooler setup, i have thought about that myself as ive got a bookmark for a company in US that will sell me a kit rated for 1200bhp for 469 dollars, im holding off on the intercooler at the moment even though ive designed my setup the best way i know until i look into it a bit more.
The aim of the car is to do it once and once only, im not going to be upgrading things i have already messed with as its a waste of time and money.
Ill admit the 5k isnt going to be achievable as i need to spend about about 3k and ive already spent 3k but the car cost 3k so if i can complete the car including buying it for 10k(1k to cover for extra bits and bobs, like w/i) i think ill have achieved something special.
Cant think of any 200mph 600bhp cars you can buy for 10k, apart from maybe an old v8 drag car!
Edited by turbotoaster on Tuesday 15th December 20:18
right bit of an update.
Spoke to reworx down south and they are happy to map the car, come with me to brunters and be a passanger with the laptop and help with my 4" exhaust.
Also spoke to STAV and he is gonna do a feature in redline when i go to brunters so it will be nice to share it with the rest of the country.
Also the budget for the car including actual buying it for 3k is 10k, im going to prove you dont need silly money to hit 200mph, its all in the parts and thinking outside the box, as you can imagine STAV loves the sound of that hence why ill get a feature
Spoke to reworx down south and they are happy to map the car, come with me to brunters and be a passanger with the laptop and help with my 4" exhaust.
Also spoke to STAV and he is gonna do a feature in redline when i go to brunters so it will be nice to share it with the rest of the country.
Also the budget for the car including actual buying it for 3k is 10k, im going to prove you dont need silly money to hit 200mph, its all in the parts and thinking outside the box, as you can imagine STAV loves the sound of that hence why ill get a feature
Been thinking about this for the last couple of months and ive decided to go for it!!
On another forum there was a debate about how much it would cost to do 200mph within 1.7miles(airfield)
The thread went a big barmy when everyone had all the little groups throwing there dummy out and a few extras pitching in for the fun, at the time i didnt really pay that much attention to it, just sort of skimmed to top of it.
Anyway while reading the one thing i picked up on was a magazine reporter from Redline, mr stav/steve. He claimed that you could go 200mph for £10k, of course everyone claimed that was rubbish but he stuck by his guns and made a few examples that made sense to me.
Yes you could build a multipurpose car that will happen to do 200mph with all the shiny alloy bits on and spend a fortune, but if you had one goal in mind and nothing else i believed it was possible.
Now i wont really turn this into a build thread as such as it will be probably be moved and id like to keep it here for everyone to see as i think this section brings in the most experience and knowledge
So a quick run down, the plan is to buy a car, tune it and make it run 200mph at brunters for £10k.
Already spent a long time chatting to guys who have done it before about this and hes give me lots of useful information and seems to back me up on this.
Spoke to Stav and hes gonna do a full magazine coverage and pay for the day etc so its a definite goer!
ill put my ideals below
The reason this car will work is that alot of the things i require are already with the car.
It has a very low drag coefficient body 0.28 which means cutting through the air is easier, it has double wishbone suspension all around which adjustable camber from factory.
I have fitted a set of tein coilovers with alloy top mounts, i got these from a friend who had only done 1000 dry miles on them for £300, this gives me the ability to make the car very low to help with aero, ie fast under, slow over creating downforce.
Now up until last year there has never been forged components for the rotary engine, its just something thats never been developed because of the complexity and the tooling cost.
This means that every power rotary engine has always used stock internals. Those 1300bhp rx7s you see at the drag strip are running the same bits that the guy up the street is running on his stock 250bhp rx7.
Now the benefit of this is the lack of parts that needs to be bought, when your going for big power on a piston engine most people 'forge' the bottom end by spending say £1k-£3k on rods, pistons and maybe a stroker crank.
Another benefit of this engine is the lack of cams, valves.
Now if you want more power from a piston engine you normally need more aggressive cams so you can get the air in and out alot easier, which can cost alot of money, some people pay up to £4k for a worked over head with lairy cams.
To do the same on a rotary all we need to do is port out the housings, now this costs anything from £200 put to £500 depending on where you go and what you have done.
For my engine, we have gone for a large port and also ported the inlet manifold, removed the extra throttle butterflies to help with flow.
This is the same as flowing the head and putting in more aggresive cams, gives the ability to make power higher in the rpms and also due to the extra flow of the port also means that the turbo will spool earlier.
Ill post this now and type the next bit up
On another forum there was a debate about how much it would cost to do 200mph within 1.7miles(airfield)
The thread went a big barmy when everyone had all the little groups throwing there dummy out and a few extras pitching in for the fun, at the time i didnt really pay that much attention to it, just sort of skimmed to top of it.
Anyway while reading the one thing i picked up on was a magazine reporter from Redline, mr stav/steve. He claimed that you could go 200mph for £10k, of course everyone claimed that was rubbish but he stuck by his guns and made a few examples that made sense to me.
Yes you could build a multipurpose car that will happen to do 200mph with all the shiny alloy bits on and spend a fortune, but if you had one goal in mind and nothing else i believed it was possible.
Now i wont really turn this into a build thread as such as it will be probably be moved and id like to keep it here for everyone to see as i think this section brings in the most experience and knowledge
So a quick run down, the plan is to buy a car, tune it and make it run 200mph at brunters for £10k.
Already spent a long time chatting to guys who have done it before about this and hes give me lots of useful information and seems to back me up on this.
Spoke to Stav and hes gonna do a full magazine coverage and pay for the day etc so its a definite goer!
ill put my ideals below
The reason this car will work is that alot of the things i require are already with the car.
It has a very low drag coefficient body 0.28 which means cutting through the air is easier, it has double wishbone suspension all around which adjustable camber from factory.
I have fitted a set of tein coilovers with alloy top mounts, i got these from a friend who had only done 1000 dry miles on them for £300, this gives me the ability to make the car very low to help with aero, ie fast under, slow over creating downforce.
Now up until last year there has never been forged components for the rotary engine, its just something thats never been developed because of the complexity and the tooling cost.
This means that every power rotary engine has always used stock internals. Those 1300bhp rx7s you see at the drag strip are running the same bits that the guy up the street is running on his stock 250bhp rx7.
Now the benefit of this is the lack of parts that needs to be bought, when your going for big power on a piston engine most people 'forge' the bottom end by spending say £1k-£3k on rods, pistons and maybe a stroker crank.
Another benefit of this engine is the lack of cams, valves.
Now if you want more power from a piston engine you normally need more aggressive cams so you can get the air in and out alot easier, which can cost alot of money, some people pay up to £4k for a worked over head with lairy cams.
To do the same on a rotary all we need to do is port out the housings, now this costs anything from £200 put to £500 depending on where you go and what you have done.
For my engine, we have gone for a large port and also ported the inlet manifold, removed the extra throttle butterflies to help with flow.
This is the same as flowing the head and putting in more aggresive cams, gives the ability to make power higher in the rpms and also due to the extra flow of the port also means that the turbo will spool earlier.
Ill post this now and type the next bit up
now when speaking to Rod(done 206mph) he mentioned to me that i would need roughly 630-650bhp to achieve 200mph, now thats in an ideal situation, ie im making that power at exactly 200mph, this brought me on to how much power do i actually need, the first thing to do is have a look around at a few compressor maps and also a few examples from the US/OZ
Now the problem with rotarys is they are very un-efficient with the airflow that they recieve, for every 10lb of air they receive they only make use of a max of 7.5lb of it.
So to make say 750bhp ill need a 1000bhp turbo if everyone follows me?
because of this un-efficent process the forces are not used fully for movement and are passed onto heat, hence why rotarys run so hot and also produce really high EGTs in turn because of the high EGTs the energy is passed out of the engine and into spooling a turbo, hence you can run a very large turbo for its engine capacity.
I did look at the garratt range of turbos but since this is very limited in budget i decided to discount them.
This left with me with a few other brands, mostly american diesel turbos. Now a company a few people may have heard off called Borg Warner are becoming increasingly popular in the performance market
Ill type up the next bit on my turbo choice in a second
Now the problem with rotarys is they are very un-efficient with the airflow that they recieve, for every 10lb of air they receive they only make use of a max of 7.5lb of it.
So to make say 750bhp ill need a 1000bhp turbo if everyone follows me?
because of this un-efficent process the forces are not used fully for movement and are passed onto heat, hence why rotarys run so hot and also produce really high EGTs in turn because of the high EGTs the energy is passed out of the engine and into spooling a turbo, hence you can run a very large turbo for its engine capacity.
I did look at the garratt range of turbos but since this is very limited in budget i decided to discount them.
This left with me with a few other brands, mostly american diesel turbos. Now a company a few people may have heard off called Borg Warner are becoming increasingly popular in the performance market
Ill type up the next bit on my turbo choice in a second
ok there are many different turbos from borg warner.
I have decided to go with a s475 which can flow 100lb/min with a 1.15 A/R rear end, i can go larger on the rear but decided this is a good compromise between spool and top end power.
I can give full specs of wheel sizes if anyone needs it
to give you an idea of size, here it is next to a coke can
It will normally outspool the equivalant GT4202 by 400rpm on a rotary and they ony cost £400-£600 from USA so a bit of a bargain!
Obviously you have this massive turbo, your gonna need to connect it to the engine, this is where a forum member on pf called rickylee comes into force.
Now after seeing his manifold he made on his turbo civic build thread, after seeing that i got in touch with him about making me a manifold, really nice chap and he will be building it, will also run a 5inch downpipe to help with spool and top end power which will exit behind the drivers side wheel.
Ill be using a 60mm wastegate and the manifold will be a t6 divided version to help out boost threshold
looks like this
I have decided to go with a s475 which can flow 100lb/min with a 1.15 A/R rear end, i can go larger on the rear but decided this is a good compromise between spool and top end power.
I can give full specs of wheel sizes if anyone needs it
to give you an idea of size, here it is next to a coke can
It will normally outspool the equivalant GT4202 by 400rpm on a rotary and they ony cost £400-£600 from USA so a bit of a bargain!
Obviously you have this massive turbo, your gonna need to connect it to the engine, this is where a forum member on pf called rickylee comes into force.
Now after seeing his manifold he made on his turbo civic build thread, after seeing that i got in touch with him about making me a manifold, really nice chap and he will be building it, will also run a 5inch downpipe to help with spool and top end power which will exit behind the drivers side wheel.
Ill be using a 60mm wastegate and the manifold will be a t6 divided version to help out boost threshold
looks like this
now your throwing an awful lot of hot air around into an engine that is known to run hot anyway.
Without proper thinking its a recipy for disaster.
The standard radiator is around 30mm thick and does a decent job for a standard car but very quickly reaches its limit once your running alot of power.
Alot of people choose to keep the stock one for a while when running single turbo, the reason for this is 2 fold.
1. because most single turbos are only oil cooled you have one less hot think to dump heat back into the water system.
2. because of the larger rear end of a single compared to the twins theres less restriction for the heat leaving the engine, this in turn helps get the heat out of the rotary engine faster, this was something i read and im sure theres a better way of typing it, but ill leave that for improvement.
Now im not just gonna run 400bhp on this engine, im looking nearly double that, so its silly to believe that the stock rad can cope.
Luckily the ebay rads you see for sale are only £120 and are proven to work on big power cars, they are 58mm thick which is a big improvement and are cheap as a bonus.
so got this one
The car runs 2 oil coolers as stock and they are pretty good at controlling oil temps even on heavily tuned rx7s.
Without proper thinking its a recipy for disaster.
The standard radiator is around 30mm thick and does a decent job for a standard car but very quickly reaches its limit once your running alot of power.
Alot of people choose to keep the stock one for a while when running single turbo, the reason for this is 2 fold.
1. because most single turbos are only oil cooled you have one less hot think to dump heat back into the water system.
2. because of the larger rear end of a single compared to the twins theres less restriction for the heat leaving the engine, this in turn helps get the heat out of the rotary engine faster, this was something i read and im sure theres a better way of typing it, but ill leave that for improvement.
Now im not just gonna run 400bhp on this engine, im looking nearly double that, so its silly to believe that the stock rad can cope.
Luckily the ebay rads you see for sale are only £120 and are proven to work on big power cars, they are 58mm thick which is a big improvement and are cheap as a bonus.
so got this one
The car runs 2 oil coolers as stock and they are pretty good at controlling oil temps even on heavily tuned rx7s.
well ill be going with a power fc, its easy to tune and pretty versatile
It arrived in the post from japan.
yes something like a autronic/motec would be better but theres some big numbers being done over in the states on this ecu and money is an issue.
The good thing about it is the commander which can monitor everything the ecu sees, saves me buying a few gauges, for example at can see all the below in real time
Engine RPM
Ignition Timing
Vehicle Speed
Air Flow Voltage (Pressure Sensor Voltage)
Injector Duty Cycle
Boost
Knocking Level
Battery Voltage
Intake Air Temp
Water Temp
Thinking about injectors i did some calculations and for 700bhp a rotary needs 5500cc/min of fuel(not 100% duty, about 85%)
now ross at dragon performace and the guys at reworx both suggested i go with 6 injectors instead of trying to fit massive injectors into the primarys and secondarys as its alot harder to map.
so we talked about maybe 6 x1000cc injectors, but then that comes down to budget again.
I was watching a guy in america running 9s quarters running a stock ecu with a peter farell piggy back ecu controlling extra injectors, he was pushing 600whp+ which is the numbers im after.
i sat and thought about it a couple a nights ago and thought how can i do it.
it then came to me, i already have 2800cc of the injectors in the car at the moment, i only need another 2700cc and im sorted, both tuners recommended 6 injectors, so why dont i put 2 x 1600cc injectors in, that 3200cc worth of fuel, more than enough, watched a few videos of some monster rx3 and he was running extra injectors in his Upper Inlet Manifold and ive decided thats where they are gonna go, on the secondary port sides(outer edges) this means i keep my stock primarys for driving around like miss daisy, also keeps my afr while idling as normal and normal driving ill be ok
Fuel pumps will be 2x 305ltr pumps running in tank which will give me more than enough fueling
It arrived in the post from japan.
yes something like a autronic/motec would be better but theres some big numbers being done over in the states on this ecu and money is an issue.
The good thing about it is the commander which can monitor everything the ecu sees, saves me buying a few gauges, for example at can see all the below in real time
Engine RPM
Ignition Timing
Vehicle Speed
Air Flow Voltage (Pressure Sensor Voltage)
Injector Duty Cycle
Boost
Knocking Level
Battery Voltage
Intake Air Temp
Water Temp
Thinking about injectors i did some calculations and for 700bhp a rotary needs 5500cc/min of fuel(not 100% duty, about 85%)
now ross at dragon performace and the guys at reworx both suggested i go with 6 injectors instead of trying to fit massive injectors into the primarys and secondarys as its alot harder to map.
so we talked about maybe 6 x1000cc injectors, but then that comes down to budget again.
I was watching a guy in america running 9s quarters running a stock ecu with a peter farell piggy back ecu controlling extra injectors, he was pushing 600whp+ which is the numbers im after.
i sat and thought about it a couple a nights ago and thought how can i do it.
it then came to me, i already have 2800cc of the injectors in the car at the moment, i only need another 2700cc and im sorted, both tuners recommended 6 injectors, so why dont i put 2 x 1600cc injectors in, that 3200cc worth of fuel, more than enough, watched a few videos of some monster rx3 and he was running extra injectors in his Upper Inlet Manifold and ive decided thats where they are gonna go, on the secondary port sides(outer edges) this means i keep my stock primarys for driving around like miss daisy, also keeps my afr while idling as normal and normal driving ill be ok
Fuel pumps will be 2x 305ltr pumps running in tank which will give me more than enough fueling
one thing i havent mentioned here aswell is that the car will be running pre-turbo water injection, im making my own kit aswell and it will be a purely mechanical system so no pumps involved, got this idea from a couple of guys in america doing it, one guy runs 23psi on pump fuel on a big turbo daily, the other runs 32psi on pump fuel and has 700bhp.
this design isnt mine but im using it to give you an idea how it works.
very simple set up, good thing is, the solenoid will open at say 1bar(depends what i set it at) and the more boost you are running, the more water, so theres no need to fiddle with jet sizes once you have set it up to flow the right amount of water
Ill be running around 2bar of boost pressure
this design isnt mine but im using it to give you an idea how it works.
very simple set up, good thing is, the solenoid will open at say 1bar(depends what i set it at) and the more boost you are running, the more water, so theres no need to fiddle with jet sizes once you have set it up to flow the right amount of water
Ill be running around 2bar of boost pressure
ok onto the deal with power, i did some gear testing yesterday to determine what needs to be done
So i went out with my gps meter to do some gear testing.
to do 100mph(gps) i need to do 4500rpm, give or take 20rpm
so to do 200mph i need to pull 9000rpm, simple maths. this is on 255/40/17s there maybe 1mph more for tyre expansion but ill leave that out to make it easier. also a 4.1 diff
So i got out my gear calculator program i have to put the numbers in to see how i can help.
online i have found that the 5th gear results are much longer than they should be, 0.719, which must be incorrect else id be doing a massive speed.
Anyway i adjusted my 5th gear till i got 100mph at 4500rpm with tyres stated earlier.
This gave me a 5 gear ratio of 0.820 or 22.15mph per 1000rpm.
Now according to what the guy with the stock port and same turbo as me did, his max power was at 8200rpm, because of my big streetport im calculating that my max power will probably be about 8500rpm.
So to do 200mph im going to be past my max power and its gonna be trailing off, not good really at that means ill have less power where i need it most.
At my maximum power ill only be doing 188mph, so well short of the mark, so lets change the diff to an auto one to see what we can do.
now this changes the speed at max power to 198mph, which is much better, very close to the mark.
Ill have to wait to see what my final max power/rpm will be but it least im making progress on gearing.
also say for example i only make max power at 8200rpm like the other guy did i can still hit 200mph with 8250mph if i change my rear tyres to 255/45/17
hope this clears up any potential confusion people have had in the past
One thing about power is if i made 1000bhp at 6k but only 500bhp at 9k and i need 9k to hit 200mph i wouldnt do it.
But if im making 1000bhp at 6k but 640bhp at 9k i would hit 200mph.
So i can make up with tyres but i may need more than 640bhp to hit my target, hence the aim of 700bhp at around 30psi.
A completely stock engine(ie built by a guy on the mazda production line)with my turbo did 709bhp at 33psi and runs 9sec quarter miles so the power is avaliable
that way if 200mph is past my peak power slightly then it still should be above 640bhp.
this was from Rod about his old saff cosworth engine which was 750bhp on gas and did 201.6mph at that power
'On my last engine Peak Power was below 7.5k but held on to about 7.7k. We pulled 8.2k so was well past peak Power. BUT we could not pull the longer gearing so this was the best compromise'
So at 200mph he wasnt putting out the power people think he has because hes gone past peak power
So i went out with my gps meter to do some gear testing.
to do 100mph(gps) i need to do 4500rpm, give or take 20rpm
so to do 200mph i need to pull 9000rpm, simple maths. this is on 255/40/17s there maybe 1mph more for tyre expansion but ill leave that out to make it easier. also a 4.1 diff
So i got out my gear calculator program i have to put the numbers in to see how i can help.
online i have found that the 5th gear results are much longer than they should be, 0.719, which must be incorrect else id be doing a massive speed.
Anyway i adjusted my 5th gear till i got 100mph at 4500rpm with tyres stated earlier.
This gave me a 5 gear ratio of 0.820 or 22.15mph per 1000rpm.
Now according to what the guy with the stock port and same turbo as me did, his max power was at 8200rpm, because of my big streetport im calculating that my max power will probably be about 8500rpm.
So to do 200mph im going to be past my max power and its gonna be trailing off, not good really at that means ill have less power where i need it most.
At my maximum power ill only be doing 188mph, so well short of the mark, so lets change the diff to an auto one to see what we can do.
now this changes the speed at max power to 198mph, which is much better, very close to the mark.
Ill have to wait to see what my final max power/rpm will be but it least im making progress on gearing.
also say for example i only make max power at 8200rpm like the other guy did i can still hit 200mph with 8250mph if i change my rear tyres to 255/45/17
hope this clears up any potential confusion people have had in the past
One thing about power is if i made 1000bhp at 6k but only 500bhp at 9k and i need 9k to hit 200mph i wouldnt do it.
But if im making 1000bhp at 6k but 640bhp at 9k i would hit 200mph.
So i can make up with tyres but i may need more than 640bhp to hit my target, hence the aim of 700bhp at around 30psi.
A completely stock engine(ie built by a guy on the mazda production line)with my turbo did 709bhp at 33psi and runs 9sec quarter miles so the power is avaliable
that way if 200mph is past my peak power slightly then it still should be above 640bhp.
this was from Rod about his old saff cosworth engine which was 750bhp on gas and did 201.6mph at that power
'On my last engine Peak Power was below 7.5k but held on to about 7.7k. We pulled 8.2k so was well past peak Power. BUT we could not pull the longer gearing so this was the best compromise'
So at 200mph he wasnt putting out the power people think he has because hes gone past peak power
Just for reference now the engine has done 900miles i took it to a dyno to see how the engine was doing.
running a very rich map(so power lost) running stock boost(10psi) pulled some timing aswell and it made 283bhp at 6900rpm.
This is 400rpm higher than stock and 30bhp more power, so at a very low boost running super rich(11:1 afr)
This shows that my ports are flowing well, id imagine with a bit of adjustment to the fuel to where the stock afr is sort the timing out another 20bhp could be gained, so thats 50bhp above stock at same boost
just need to do a compression test to check everything is bed in correctly and then start saving more money to start putting things together
running a very rich map(so power lost) running stock boost(10psi) pulled some timing aswell and it made 283bhp at 6900rpm.
This is 400rpm higher than stock and 30bhp more power, so at a very low boost running super rich(11:1 afr)
This shows that my ports are flowing well, id imagine with a bit of adjustment to the fuel to where the stock afr is sort the timing out another 20bhp could be gained, so thats 50bhp above stock at same boost
just need to do a compression test to check everything is bed in correctly and then start saving more money to start putting things together
since this is my thread, i thought id do a little rotary porting 101 if people are still reading.
to understand a rotary engine you have the imagine, how could i make my engine simpler, what things limit me when im making power(naturally asp)
Well first we look at cams, stock cams are normally pretty mild, with low lift and short duration, so, they dont allow the valves to open much or for long......doesnt allow much space to get that air in there does it.
So we change over to a more aggressive cam which does it....more power!
then we move onto the head, because yes the valves are nice and open but the air still needs to get down to them by passing down a small hole, increase the size of that hole(port) means we can more of that valuable air to the valves.
now from reading that you understand the basic principles of piston engine tuning.
Now a rotary isnt some magical engine run on leprechauns and peanut butter, it must follow the same rulls as a piston engine.
But how it does this well....it swaps all that for just a hole, thats right, the cams, valves, valve springs, head.
Now i wont go into detail on how a rotary works, ill just explain how to tune them.
Before reading anything else below i suggest you watch this as i found this explains how a rotary works very well so everybody should understand it
http://www.youtube.com/watch?v=oGrD7...eature=rela...
Ok now you have watched it ill continue on.
As you saw in the video, the rotor has 3 sides, to make it easier, ill call the first side, SIDE 1.
the port where the fuel/air comes in is opened by one end of the SIDE 1, the air/fuel comes in, then is closed off by the other end of SIDE 1.
So you have an opening and a closing, just like you do with a cam to open and close valves.
Now this below is a typical stock port, the one you find on standard rx7s
when the rotor moves to reveal the port(open) the first part that is opened is the long left hand side edge, the mixture comes into the chamber and then the other end of the rotor closes the port at the top horizontal edge as it rotates.
So by making the hole larger in different areas you can affect when the port will be open and also when it will be closed.
these are 2 pics of my templates over stock ports so you can see what i have done to my engine
this is my secondary port(ie big one to help with high rpm)
as you can see i am making it open earlier a little bit, if you go to far you get overlap so loose to much low down power, but then you can see i have increased it alot at the top of the port(closing) this is to help get the air into the engine, ie wait as long as possible before the port closes, this like duration on cams.
One last thing you should notice is the stock port has a flat top and mine is a curve, this is to help the engine make the power a little bit lower down and give me a wider torque curve, if it was straight it would close instantly instead of a lower close and a faster close means you make maximum power higher in the rpm.
Since the engine needs to be useful for many different things i found it would be best to not make a 10krpm screamer.
now this is my primary port, this is the one that the fuel goes down when in driving like miss daisy and generally pootling around.
Now because of i want the car to run around nicely on the street i want to keep this mild.
Now as you can see the out edge is ported much larger than the secondary port above, the reason for is the port is smaller than the other so i have more room to increase it without getting overlap.
if you compare the pictures apart from the length, they are the same width, showing that both ports now open and close at the same time.
Now thats the port timing done(like fitting cams) now because as you can see i have had to increase the size of the ports to get the timing right i have also allowed much more air to pass through because of there physical size....this is like porting out a head for it to flow more.
Pretty simple really, buy a dremel and a porting kit from b&q and do it yourself, does the same thing as porting a head and buying a set of expensive cams, valves, valve springs
to understand a rotary engine you have the imagine, how could i make my engine simpler, what things limit me when im making power(naturally asp)
Well first we look at cams, stock cams are normally pretty mild, with low lift and short duration, so, they dont allow the valves to open much or for long......doesnt allow much space to get that air in there does it.
So we change over to a more aggressive cam which does it....more power!
then we move onto the head, because yes the valves are nice and open but the air still needs to get down to them by passing down a small hole, increase the size of that hole(port) means we can more of that valuable air to the valves.
now from reading that you understand the basic principles of piston engine tuning.
Now a rotary isnt some magical engine run on leprechauns and peanut butter, it must follow the same rulls as a piston engine.
But how it does this well....it swaps all that for just a hole, thats right, the cams, valves, valve springs, head.
Now i wont go into detail on how a rotary works, ill just explain how to tune them.
Before reading anything else below i suggest you watch this as i found this explains how a rotary works very well so everybody should understand it
http://www.youtube.com/watch?v=oGrD7...eature=rela...
Ok now you have watched it ill continue on.
As you saw in the video, the rotor has 3 sides, to make it easier, ill call the first side, SIDE 1.
the port where the fuel/air comes in is opened by one end of the SIDE 1, the air/fuel comes in, then is closed off by the other end of SIDE 1.
So you have an opening and a closing, just like you do with a cam to open and close valves.
Now this below is a typical stock port, the one you find on standard rx7s
when the rotor moves to reveal the port(open) the first part that is opened is the long left hand side edge, the mixture comes into the chamber and then the other end of the rotor closes the port at the top horizontal edge as it rotates.
So by making the hole larger in different areas you can affect when the port will be open and also when it will be closed.
these are 2 pics of my templates over stock ports so you can see what i have done to my engine
this is my secondary port(ie big one to help with high rpm)
as you can see i am making it open earlier a little bit, if you go to far you get overlap so loose to much low down power, but then you can see i have increased it alot at the top of the port(closing) this is to help get the air into the engine, ie wait as long as possible before the port closes, this like duration on cams.
One last thing you should notice is the stock port has a flat top and mine is a curve, this is to help the engine make the power a little bit lower down and give me a wider torque curve, if it was straight it would close instantly instead of a lower close and a faster close means you make maximum power higher in the rpm.
Since the engine needs to be useful for many different things i found it would be best to not make a 10krpm screamer.
now this is my primary port, this is the one that the fuel goes down when in driving like miss daisy and generally pootling around.
Now because of i want the car to run around nicely on the street i want to keep this mild.
Now as you can see the out edge is ported much larger than the secondary port above, the reason for is the port is smaller than the other so i have more room to increase it without getting overlap.
if you compare the pictures apart from the length, they are the same width, showing that both ports now open and close at the same time.
Now thats the port timing done(like fitting cams) now because as you can see i have had to increase the size of the ports to get the timing right i have also allowed much more air to pass through because of there physical size....this is like porting out a head for it to flow more.
Pretty simple really, buy a dremel and a porting kit from b&q and do it yourself, does the same thing as porting a head and buying a set of expensive cams, valves, valve springs
well bit of a small random update, since i got the apexi ecu ive just celotaped it to where my pocket pc is on the left hand side of the gearstick, this was just to monitor is on friday while i top up with fuel and let the ecu learn the idle.
The issue was that it was so far away from my line of sight that i had to take my eyes well away from the road to monitor it, now after neally driving into a curb last night while watching my knock readings i decided its better to look for something to attach it to sooner rather than later.
Ill also need it for my top speed runs and i dont want to be looking away from the tarmac for that
So i theres the r magic power fc holder from japan but they are £50 and thats alot for just a piece of plastic, so i started looking at the commander and thought, well its the shape of a phone, why dont i just get a phone holder.
so i started searching the net for one, i found a few that attach to the windscreen but didnt fancy that as people might think its a sat nav and smash my car open when i go to tesco etc.
then i saw the ones that fit to your air vents, better i thought so i sat in the car and looked straight head to see if the vents were in my eye line, not quite.
so i looked at my dash, and thought where is the best place to put it, well i dont smoke and where the cigarette lighter would be good.
so i sat and made a little design on a scrap piece of paper and commited to making myself one during this week.
Anyway i was walking around tesco today and walked past the mobile phone part, decided to have a quick look and what do you know, they had the perfect thing.
Also as an added bonus they reduced them down from £6.84 to £1.99!!
So snapped it up and took it home.
first things first, cut of the little charger cable that i dont need.
where fag lighter is
attached commander to holder
plug into fag lighter and adjust height
check visability...seems good
turn lights on for night mode
a day full on win it seems.
anything that helps me stay in budget is a good day for me
The issue was that it was so far away from my line of sight that i had to take my eyes well away from the road to monitor it, now after neally driving into a curb last night while watching my knock readings i decided its better to look for something to attach it to sooner rather than later.
Ill also need it for my top speed runs and i dont want to be looking away from the tarmac for that
So i theres the r magic power fc holder from japan but they are £50 and thats alot for just a piece of plastic, so i started looking at the commander and thought, well its the shape of a phone, why dont i just get a phone holder.
so i started searching the net for one, i found a few that attach to the windscreen but didnt fancy that as people might think its a sat nav and smash my car open when i go to tesco etc.
then i saw the ones that fit to your air vents, better i thought so i sat in the car and looked straight head to see if the vents were in my eye line, not quite.
so i looked at my dash, and thought where is the best place to put it, well i dont smoke and where the cigarette lighter would be good.
so i sat and made a little design on a scrap piece of paper and commited to making myself one during this week.
Anyway i was walking around tesco today and walked past the mobile phone part, decided to have a quick look and what do you know, they had the perfect thing.
Also as an added bonus they reduced them down from £6.84 to £1.99!!
So snapped it up and took it home.
first things first, cut of the little charger cable that i dont need.
where fag lighter is
attached commander to holder
plug into fag lighter and adjust height
check visability...seems good
turn lights on for night mode
a day full on win it seems.
anything that helps me stay in budget is a good day for me
Thanks for taking the time to explain it all so well too.
Really enjoying this read! I'm also looking to get an RX7 in the next months and do a few changes (though not chasing anywhere near your figures, maybe 350bhp) while still keeping drivability so its good to know the full ins and outs of whats going on. Especially with the ports thanks again.
This is a great thread - although I have to say very very few cars can pull 200mph at brunters so if you do it, well done indeed. There seems to be a massive gap between theory and reality when it comes to actually breaking the 200mph mark - I'd love to see your car do it because RX7s are fab motors.
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