Big cams, OE manifold, way down on power.
Discussion
One for our resident feral cat to get his teeth into maybe 
Sorry, a bit of a long one, i'll split it into two short/long sections for the knowledgeable/patient and snowflake/Millenials.
Short story/question:
From a power perspective only is there any reason why and how smaller cams would give more top end power than 'big' ones in conjunction with a modern convoluted plastic OEM manifold?
Is it just my exhaust cam which is too long on duration, would a shorter duration one give more top end?
Long story:
Basically I've come from a turbo background, but am now going the other way and getting my head around N/A engines. I'm building up my knowledge base by starting at the bottom and adding bits on to see what does what.
I make some of the parts myself and bolt them on, they can be used on other iterations too so it's not like i'm throwing thousands at it then putting the parts in the bin when they don't work.
Car is a 1 ton track car.
The engine i'm working with is a reasonably modern (mid noughties), 2.3ltr 16v. Port injection, single VVT now removed.
The spec so far is:
12:1 CR working with 99 Ron
Mild porting to the already excellent head.
OE valves 30 and 35mm
Inlet cam of 12mm and 276 @ .1mm
Ex cam of 11 and 302 @ .1 (Yes I know)
Both intake and inlet valves are 3mm open at TDC so plenty of overlap, as you can imagine it ticks over like a POS at 1200-1500rpm. I do have angles jotted down if needed.
4 - 1 manifold, 1.8"/45mm externally going into a 60mm exit merge then to a 3" exhaust. (hoping that some venturi effect happens here!), it's an 'off-the-shelf' mani hence 60mm exit.
The inlet manifold is really the only thing which remains untouched, TB is 60mm. It has two sets of runners and i'm going to call them long and short, but in reality and interestingly what the internal runner flaps do is change it from 4 long runners to all 8 (4 short, 4 long) open. Original manifold runner control strategy was; short - long - short throughout the rev range. We call this IMRC.
Long runners are approx 16", short are 12" + port length, neither is straight, both curl round a bit.
It's been mapped twice:
Red lines are first session, green is second session.
Second session was with the ex cam retarded more, it was 2mm open at TDC, is now 3mm like the inlet. Also it was with a 3" exhaust, red run was with 60mm. Sorry for mixing my units. Much of those gains in the 5000 to 6500 region were actually from playing with the IMRC.
As you can see we did make some large improvements in one part of the range, but it still flatlines at high rpm and gives almost the same max output. In it's original road going format the engine puts out about 163bhp. I do have the WHP graph too.
Initially it appears to be the manifold which is the problem from 6k onwards.
Fuelling isn't an issue.
Would a smaller cam and less overlap give more peak power and if so, how or why? It's been suggested it would based on measured manifold pressure, this is the bit i'm struggling to understand, as I see it now I've done everything to create a 250bhp engine, but the manifold is strangling it as it's too restrictive and the pipe lengths are wrong. I know separate TBs are the way to go and ultimately that is what it will get once i've been through everything else.
You might wonder why i've done XY & Z, but there are generally good explanations for this.
My next move is to fab up a simplified inlet manifold with short straight runners, a plenum, the OE 60mm TB and keep the cams or maybe fit some smaller cams with this manifold, but as per above, cams i'm not sure about.
After that will be the more expensive route of ITBs.
Any useful input appreciated.
Sorry, a bit of a long one, i'll split it into two short/long sections for the knowledgeable/patient and snowflake/Millenials.
Short story/question:
From a power perspective only is there any reason why and how smaller cams would give more top end power than 'big' ones in conjunction with a modern convoluted plastic OEM manifold?
Is it just my exhaust cam which is too long on duration, would a shorter duration one give more top end?
Long story:
Basically I've come from a turbo background, but am now going the other way and getting my head around N/A engines. I'm building up my knowledge base by starting at the bottom and adding bits on to see what does what.
I make some of the parts myself and bolt them on, they can be used on other iterations too so it's not like i'm throwing thousands at it then putting the parts in the bin when they don't work.
Car is a 1 ton track car.
The engine i'm working with is a reasonably modern (mid noughties), 2.3ltr 16v. Port injection, single VVT now removed.
The spec so far is:
12:1 CR working with 99 Ron
Mild porting to the already excellent head.
OE valves 30 and 35mm
Inlet cam of 12mm and 276 @ .1mm
Ex cam of 11 and 302 @ .1 (Yes I know)
Both intake and inlet valves are 3mm open at TDC so plenty of overlap, as you can imagine it ticks over like a POS at 1200-1500rpm. I do have angles jotted down if needed.
4 - 1 manifold, 1.8"/45mm externally going into a 60mm exit merge then to a 3" exhaust. (hoping that some venturi effect happens here!), it's an 'off-the-shelf' mani hence 60mm exit.
The inlet manifold is really the only thing which remains untouched, TB is 60mm. It has two sets of runners and i'm going to call them long and short, but in reality and interestingly what the internal runner flaps do is change it from 4 long runners to all 8 (4 short, 4 long) open. Original manifold runner control strategy was; short - long - short throughout the rev range. We call this IMRC.
Long runners are approx 16", short are 12" + port length, neither is straight, both curl round a bit.
It's been mapped twice:
Red lines are first session, green is second session.
Second session was with the ex cam retarded more, it was 2mm open at TDC, is now 3mm like the inlet. Also it was with a 3" exhaust, red run was with 60mm. Sorry for mixing my units. Much of those gains in the 5000 to 6500 region were actually from playing with the IMRC.
As you can see we did make some large improvements in one part of the range, but it still flatlines at high rpm and gives almost the same max output. In it's original road going format the engine puts out about 163bhp. I do have the WHP graph too.
Initially it appears to be the manifold which is the problem from 6k onwards.
Fuelling isn't an issue.
Would a smaller cam and less overlap give more peak power and if so, how or why? It's been suggested it would based on measured manifold pressure, this is the bit i'm struggling to understand, as I see it now I've done everything to create a 250bhp engine, but the manifold is strangling it as it's too restrictive and the pipe lengths are wrong. I know separate TBs are the way to go and ultimately that is what it will get once i've been through everything else.
You might wonder why i've done XY & Z, but there are generally good explanations for this.
My next move is to fab up a simplified inlet manifold with short straight runners, a plenum, the OE 60mm TB and keep the cams or maybe fit some smaller cams with this manifold, but as per above, cams i'm not sure about.
After that will be the more expensive route of ITBs.
Any useful input appreciated.
stevesingo said:
What engine exactly and pics of the manifold would help. Bore/Stroke? Cam open and closing timing.
The exhaust cam is probably a bit strong.
IME of the BMW S14B25 2.5lt 4cyl, 95/87mm bore stroke, it generally wants more intake cam than exhaust. My engine has 292deg @ 0.1mm intake and 284deg @ 0.1mm with 4.5/3.5mm lift at TDC. It idles rock solid at 950rpm and I can pull away in 2nd without touching the throttle.
Other things to consider are that as cams get more aggressive, the more sensitive the engine is to intake and exhaust length.
But in this case, I think much too much exhaust cam.
Yes I agree, it was designed by computer, flies in the face of conventional wisdom and is probably wrong, but that's how I arrived at it. Whilst it's unsurprisingly causing idle issues, I don't know for sure if it's lowering the top end power, that's the issue, you are probably running ITBs? Valvetronic, VVT?The exhaust cam is probably a bit strong.
IME of the BMW S14B25 2.5lt 4cyl, 95/87mm bore stroke, it generally wants more intake cam than exhaust. My engine has 292deg @ 0.1mm intake and 284deg @ 0.1mm with 4.5/3.5mm lift at TDC. It idles rock solid at 950rpm and I can pull away in 2nd without touching the throttle.
Other things to consider are that as cams get more aggressive, the more sensitive the engine is to intake and exhaust length.
But in this case, I think much too much exhaust cam.
There isn't much to be gained by looking at a manifold like this, not without cutting it into multiple pieces.
Edited by 227bhp on Monday 13th January 21:20
DeadCatWalking said:
The exhaust cam is ridiculous. If a computer program came up with that then it needs scrapping. Much of the combustion power is going straight down the exhaust pipe because the exhaust valves are opening far too early. Same exhaust duration as inlet would be plenty. LCA is way out also. The engine probably needs about 105 degrees timed 3 degrees advanced so 102 ATDC full lift on inlet and 108 BTDC on exhaust with the right cams.
I agree and moreover, after suspecting it was wrong I now have proof so will get my money back.So you think the ex cam is actually losing power?
If it is i'll get another, the 11mm lift matches the springs, I can go to 12mm and change the springs if it would be worth it, but not sure an extra 1mm would do much on the exhaust.
DeadCatWalking said:
Exhaust manifold is sized for about 260 bhp and should need a 2 1/2" o/d exhaust. 3" is too big.
https://web.archive.org/web/20110918115047/http://...
https://web.archive.org/web/20110903091024/http://...
The exhaust is debatable and others would disagree. As I see it it's not costing me power, it was done so it couldn't be suspected of holding the engine back.https://web.archive.org/web/20110918115047/http://...
https://web.archive.org/web/20110903091024/http://...
DeadCatWalking said:
Inlet cam should suffice for about 100 bhp/litre.
It's pointless speculating about the potential of the plenum system. If you want 100 bhp/litre then fit TBs.
It's pointless speculating about the potential of the plenum system. If you want 100 bhp/litre then fit TBs.
As outlined there is a halfway house here, it would be interesting to see what a better design of manifold brings to the party. What I didn't say was that is has drive by wire (electronic throttle), so a lot to be lost and a lot of money to be found to get rid of it.
DeadCatWalking said:
Main problem is lack of torque. 75 ish ft lbs per litre is not very good. Should be over 90 with proper pulse tuning and the right exhaust cam.
Ok, as per above, i'll get another cam.stevesingo said:
227bhp said:
Yes I agree, it was designed by computer, flies in the face of conventional wisdom and is probably wrong, but that's how I arrived at it. Whilst it's unsurprisingly causing idle issues, I don't know for sure if it's lowering the top end power, that's the issue.
Bore is 87.5 and Stroke 94 so a completely different long stroke compared to yours, but you are probably running ITBs? Valvetronic, VVT?
There isn't much to be gained by looking at a manifold like this, not without cutting it into multiple pieces:
No VTT, but I do have ITBs, but in regard to idle quality, this should not be a differentiator. My EMS uses TPS for load calculation. What are you using? MAP and MAF can suffer at low rpm with long duration cams.Bore is 87.5 and Stroke 94 so a completely different long stroke compared to yours, but you are probably running ITBs? Valvetronic, VVT?
There isn't much to be gained by looking at a manifold like this, not without cutting it into multiple pieces:
WHat is the origin of the engine. There maybe schematic images of the intake online however moot that may be. Just get to TBs.
As per my last post If I ditch the DBW throttle i'll lose everything else it brings to the party, i'll take it one step at a time.
It isn't all about the end result, it's about the journey too.
Inline__engine said:
if you want an engine sim then use ENGMOD4T and the new version of pipemax.
this engine looks like it was designed based on 2V/cyl push rod engines meant for drag racing.....
if you tell us
bore
stroke
rod length
cylinder head inlet valve size and flow
cylinder head exaust valve size and flow
type of characteristcs you want, street, race, plus powerband etc
can run some basic numbers
I have the latest Pipemax now, it's very hard work and also has bugs in it. I'm hoping to get my head around it soon.this engine looks like it was designed based on 2V/cyl push rod engines meant for drag racing.....
if you tell us
bore
stroke
rod length
cylinder head inlet valve size and flow
cylinder head exaust valve size and flow
type of characteristcs you want, street, race, plus powerband etc
can run some basic numbers
The problem with a lot of these programs is they depend on the paying customer to iron out the faults for them!
DeadCatWalking said:
227bhp said:
So you think the ex cam is actually losing power?
Which bit of "Much of the combustion power is going straight down the exhaust pipe" was unclear?My best guess is that exhaust cam is costing 10-20 bhp.
227bhp said:
The exhaust is debatable and others would disagree. As I see it it's not costing me power, it was done so it couldn't be suspected of holding the engine back.
How dare you disagree with me or quote pretenders to my throne who do! I am a tuning god. Overly large exhausts (both manifolds and systems) almost always cost power and more importantly torque. Read the articles again.Manifolds are more important than systems but both can hurt if oversized.
I've read your articles before, the exhaust one states " this article considers the ideal diameter of exhaust system to be non restrictive for a given power output."
It makes no mention at all that going too big will hurt power, maybe it needs an updated version
I agree a manifold can lose power, but don't think a big exhaust can. There have always been high powered engines at the top of their game with no exhausts at all. As I see it it's there to carry a cat and the fumes and noise to the back of the car and reduce the noise on the way without being restrictive.
The graphs bear this out, there was practically zero difference to max bhp going from 60 to 75mm.
You can have a minimum, not a maximum.
The car came with 160bhp and a 60mm system as standard, why did they do that when they could have used your recommended 50mm? It would have saved them a lot of money and made the car lighter.
Edited by 227bhp on Sunday 12th January 11:31
Inline__engine said:
227bhp said:
I have the latest Pipemax now, it's very hard work and also has bugs in it. I'm hoping to get my head around it soon.
The problem with a lot of these programs is they depend on the paying customer to iron out the faults for them!
i just ran some numbers after i found most info except head flow. no bugs foundThe problem with a lot of these programs is they depend on the paying customer to iron out the faults for them!
what engine is this?
throwing some stuff at pipemax with guestimations suggested a duration in the order of ~230-235 at 1.0mm for both inlet and exhaust for a 250hp engine goal. and primary of 1-5/8" and 2-3/8" tailpipe. this means for something 180bhp currently its way out to lunch.
DeadCatWalking said:
227bhp said:
, why did they do that when they could have used your recommended 50mm?
I said 2/1/2" which is not 50 mm.System O/D
Inches System O/D
MM Max Power Output
BHP
1 5/8" 41.3mm 104
1 3/4" 44.5mm 122
1 7/8" 47.6mm 141
2" 50.8mm 162
2 1/8" 54.0mm 184
2 1/4" 57.1mm 208
2 3/8" 60.3mm 233
2 1/2" 63.5mm 260
2 5/8" 66.7mm 288
2 3/4" 69.9mm 318
2 7/8" 73.0mm 349
3" 76.2mm 381
3 1/8" 79.4mm 415
3 1/4" 82.5mm 450
3 3/8" 85.7mm 487
3 1/2" 88.9mm 525
3 5/8" 92.1mm 565
3 3/4" 95.3mm 606
3 7/8" 98.4mm 648
4" 101.6mm 692
AW111 said:
If you think the exhaust is just there to hold the muffler on you're never going to get anywhere.
FWIW I have 160 bhp from 1.6 litres, with a 2-1/4" exhaust, which lines up well with the cat's numbers.
That's a street engine with cat & muffler.
I designed the exhaust using a spreadsheet I wrote, after reading everything I could, and talking to people a lot more knowledgeable than me, and compared the numbers with similar engines as a sanity check.
A lot of US tuning books are based on 4 cyl engines being 1/2 a pushrod 2v v8, and give questionable numbers, to say the least.
Why when you could have fitted a 2" system?FWIW I have 160 bhp from 1.6 litres, with a 2-1/4" exhaust, which lines up well with the cat's numbers.
That's a street engine with cat & muffler.
I designed the exhaust using a spreadsheet I wrote, after reading everything I could, and talking to people a lot more knowledgeable than me, and compared the numbers with similar engines as a sanity check.
A lot of US tuning books are based on 4 cyl engines being 1/2 a pushrod 2v v8, and give questionable numbers, to say the least.
https://web.archive.org/web/20110903091024/http://...
2 1/4 is for 208bhp
Why does my 160bhp road car have a 60mm exhaust as standard when it should be 50?
No-one is looking at US V8 tuning books.
Read the first post properly and study the graphs, the bigger exhaust made from between a gain to zero loss where it matters most.
These guys need to go as quickly as possible no matter what, they have no exhausts:
Edited by 227bhp on Sunday 12th January 13:42
GreenV8S said:
stevieturbo said:
And it seems admin have done it again....
You sure? I assume you're referring to the cat with nine lives. The profile looks the same as normal.Anyhow, Stevie has a special hotline to him so is probably right; oh bugger
Inline__engine said:
227bhp said:
You can't accurately model this manifold that's the biggest issue.
you don't need to in order to work out the cam and exhaust ballpark recommendations, its not a simulation. one of the outputs is the recommended runner lengths.In any case lets be real the exhaust is way oversize for a 190 bhp engine, its probably good for something 260-280 bhp and something more suitable would drastically improve the driveability of the engine but thats based on the current hp number which is clearly much lower than your expectations.
Having said that its unlikely its the exhaust side costing the top end issues and causing the power plateau (almost constant power 6000-7500) which is almost certainly inlet side related due to a restriction.
i'd be going to a proper ITB setup with a bunch of different trumpet length and remap as one way or another this is the plan anyway. once you've got the inlet working properly then you can revisit the exhaust cam and exhaust depending how close you get to the 250bhp number. what has been done to head in terms of valve jobs, porting etc is the said engine know to have a adequate cylinder head?
The head is very capable, much of this is outlined in the first post which contains a lot of info that many have ignored.
PM does ask for manifold specs and does list a variable runner type, but who would have thought a manifold with the choice of 4 long and 4 short would have gone all 8 open at low rpm? It defies conventional thinking.
stevesingo said:
There is not a lot to revisit here. The engine appears to be either a 2.3 Duratec or 2.3 Mazda L Series. It is a well trodden path with various amatures such as Cosworth and Mountune having a go at improving it. Maybe there is more to give, I don't know.
If this is a learning exercise, then the best lesson is to not reinvent the wheel.
Maybe I should have rung Cosworth up and asked them to spec me an engine for me to build myself? I'm sure they would have obliged If this is a learning exercise, then the best lesson is to not reinvent the wheel.
I'm not trying to reinvent the wheel here, what is the limit of that incredibly complex manifold? You don't know for sure and no-one else is going to donate info on it for free, but I will know. That's education and it doesn't come easy, nor cheap.
It's a completely new avenue and engine for me, so really I haven't done badly by letting something spec me an exhaust cam with too much duration.
Inline__engine said:
Saying the head is ported / excellent is not really a quantitative description. Flow numbers, velocities and areas mean something though.
The different manifold options don’t change the exhaust and cam recommendations anything meaningfully provided you dont choose something out of left field like a dual plane carb. The loss of VE % can be estimated by using the factory engine to correlate other wise 5% wouldnt be too far off something build relatively recently
I have all of that info and am currently putting it into the PM program.The different manifold options don’t change the exhaust and cam recommendations anything meaningfully provided you dont choose something out of left field like a dual plane carb. The loss of VE % can be estimated by using the factory engine to correlate other wise 5% wouldnt be too far off something build relatively recently
The issue now lies in the manifold, that is the unknown factor now and as far as I can see only putting another ex cam in and putting back on the dyno will see that one put to bed.
Edited by 227bhp on Tuesday 14th January 10:14
stevesingo said:
Do you have the ability to measure MAP? Two reasons;
1, Progressively dropping MAP as RPM rises indicates a restriction. I would expect a less than 5kPa drop.
2, Measuring the fluctuations in MAP at low RPM would indicate reversion issues. If you can log it at a high frequency.
The low rpm running I would put down to the inability of the EMS to deal with reversion. Be that MAP for load sensing or MAF.
Yes it was mentioned in the first post 1, Progressively dropping MAP as RPM rises indicates a restriction. I would expect a less than 5kPa drop.
2, Measuring the fluctuations in MAP at low RPM would indicate reversion issues. If you can log it at a high frequency.
The low rpm running I would put down to the inability of the EMS to deal with reversion. Be that MAP for load sensing or MAF.
227bhp said:
Would a smaller cam and less overlap give more peak power and if so, how or why? It's been suggested it would based on measured manifold pressure, this is the bit i'm struggling to understand, as I see it now I've done everything to create a 250bhp engine, but the manifold is strangling it as it's too restrictive and the pipe lengths are wrong. I know separate TBs are the way to go and ultimately that is what it will get once i've been through everything else.
There will be logs of intake pressures via MAP we've logged most things.Also outlined earlier, for the purposes of this thread we aren't interested in low speed running right now. We know the cams and lack of ITBs are causing issues there, they were always going to, we will address those issues later.
As also said earlier, I want to find out the limits of this manifold as it has a lot of features which are very useful. Comparing what i'm doing with what others have done is utterly useless, the industry is full of bulls
t, hidden agendas and secrecy, you have to do your own R&D to sort out what is what.Inline__engine said:
227bhp said:
I have all of that info and am currently putting it into the PM program.
The issue now lies in the manifold, that is the unknown factor now and as far as I can see only putting another ex cam in and putting back on the dyno will see that one put to bed.
i think the manifold is likely the issue. i dont see 30* less ex duration adding 40+bhp at the topendThe issue now lies in the manifold, that is the unknown factor now and as far as I can see only putting another ex cam in and putting back on the dyno will see that one put to bed.
Edited by 227bhp on Wednesday 15th January 15:04
stevesingo said:
227bhp said:
There will be logs of intake pressures via MAP we've logged most things.
Also outlined earlier, for the purposes of this thread we aren't interested in low speed running right now. We know the cams and lack of ITBs are causing issues there, they were always going to, we will address those issues later.
As also said earlier, I want to find out the limits of this manifold as it has a lot of features which are very useful. Comparing what i'm doing with what others have done is utterly useless, the industry is full of bullst, hidden agendas and secrecy, you have to do your own R&D to sort out what is what.
Ref the bolded part, can you explain why you think the lack of ITBs are causing idle/low rpm issues?Also outlined earlier, for the purposes of this thread we aren't interested in low speed running right now. We know the cams and lack of ITBs are causing issues there, they were always going to, we will address those issues later.
As also said earlier, I want to find out the limits of this manifold as it has a lot of features which are very useful. Comparing what i'm doing with what others have done is utterly useless, the industry is full of bulls
t, hidden agendas and secrecy, you have to do your own R&D to sort out what is what.Any reversion and also the pulses whether they be intake or exhaust can't get back up the runners and destroy the smooth idle.
Outside of that, would your car pass an MOT on emissions?
GreenV8S said:
stevesingo said:
Ref the bolded part, can you explain why you think the lack of ITBs are causing idle/low rpm issues?
Perhaps in the sense that the cams are causing them and ITBs would resolve them.
stevesingo said:
227bhp said:
You outlined it earlier in the thread that you yourself have a car with large cams and ITBs which idles perfectly. The reason for that (as pointed out earlier) is your ITBs.
Any reversion and also the pulses whether they be intake or exhaust can't get back up the runners and destroy the smooth idle.
Outside of that, would your car pass an MOT on emissions?
You are not explaining why the you think ITBs help low speed running, you are just saying because my engine on long cams with ITBs idles fine, it must be the ITBs. But it may be for other reasons, such as the load reference the ECU is using. What are you ECU are you using and what load reference?Any reversion and also the pulses whether they be intake or exhaust can't get back up the runners and destroy the smooth idle.
Outside of that, would your car pass an MOT on emissions?
My car passes MOTs just fine.
"Any reversion and also the pulses whether they be intake or exhaust can't get back up the runners and destroy the smooth idle."It's using the OE ECU. I can't answer the other as it's out of my knowledge base, I just let them get on with it, but can find out if it's relevant..
Edited by 227bhp on Wednesday 15th January 18:50
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