What engine for a MK1, naturally aspirated?
Discussion
Probably a slightly unusual scenario which is why I haven't quite found my answer by searching yet.
Long story short, I'm moving house in the next couple of weeks and once the whole up-eval of moving is out of the way, I'd like to make use of the large garage for a project and I'm pretty certain that will be MK1 MX5 shaped.
Here's where it gets a bit odd, I think I want to buy an engine to tinker with first and buy a suitable car to drop it into in a few months time, maybe next winter.
On the engine front I've owned a standard 1.6 before and driven a few 1.8's. I know for a fact that I'd like a little more urgency than either of the standard lumps are going to offer me. I also know that I don't want a turbo. I'm generally not a fan of any forced induction though I was more open to the idea of a supercharger but a bit of research tells me that route isn't as simple as it maybe once was and certainly isn't especially cheap either.
So where I've ended up is that I want to go naturally aspirated. I realise that I will never get anywhere near the power levels of the FI engines on a like for like cost basis but that isn't the point for me. I just want a characterful, revvy engine, great throttle response and a raspy engine note. Somewhere in the 140-150 bhp range should suit me for now (they all say that, I know).
So the plan is to for Jenvey throttle bodies (because I love independent throttle bodies) with the bare minimum in other components to get that set up working, which will probably mean, intake manifold, throttle pot and linkage, a map sensor and a megasquirt. I'll put a nice exhaust on too but you can see it's already getting expensive!
The big question and why I'm starting this thread is what engine I'm going to bolt it all onto? Reading around on here and MX5 nutz, it seems like a good combo would be a Mk2.5 1.8 VVT block with a MK2 1.8 head. I understand the VVT block has centre crank support making it a good basis for future tuning. The MK2 head, I'm not sure of the benefits but it seems to be the chosen route by many. Does this sound like a good plan? Is it naive to assume these two mate seamlessly together and will drop straight into a MK1 engine bay like they were made to match?
I should add, that though I'll do all of the basics, at this stage I don't envisage carrying out any major engine surgery. I realise there are benefits to be had from playing around with the valves, porting, skimming etc to get it revving a little higher but I think that may have to wait for another day, or more accurately another pay day.
I have lots of further questions but I can see this already a very long winded question so I'll leave it there for now.
Long story short, I'm moving house in the next couple of weeks and once the whole up-eval of moving is out of the way, I'd like to make use of the large garage for a project and I'm pretty certain that will be MK1 MX5 shaped.
Here's where it gets a bit odd, I think I want to buy an engine to tinker with first and buy a suitable car to drop it into in a few months time, maybe next winter.
On the engine front I've owned a standard 1.6 before and driven a few 1.8's. I know for a fact that I'd like a little more urgency than either of the standard lumps are going to offer me. I also know that I don't want a turbo. I'm generally not a fan of any forced induction though I was more open to the idea of a supercharger but a bit of research tells me that route isn't as simple as it maybe once was and certainly isn't especially cheap either.
So where I've ended up is that I want to go naturally aspirated. I realise that I will never get anywhere near the power levels of the FI engines on a like for like cost basis but that isn't the point for me. I just want a characterful, revvy engine, great throttle response and a raspy engine note. Somewhere in the 140-150 bhp range should suit me for now (they all say that, I know).
So the plan is to for Jenvey throttle bodies (because I love independent throttle bodies) with the bare minimum in other components to get that set up working, which will probably mean, intake manifold, throttle pot and linkage, a map sensor and a megasquirt. I'll put a nice exhaust on too but you can see it's already getting expensive!
The big question and why I'm starting this thread is what engine I'm going to bolt it all onto? Reading around on here and MX5 nutz, it seems like a good combo would be a Mk2.5 1.8 VVT block with a MK2 1.8 head. I understand the VVT block has centre crank support making it a good basis for future tuning. The MK2 head, I'm not sure of the benefits but it seems to be the chosen route by many. Does this sound like a good plan? Is it naive to assume these two mate seamlessly together and will drop straight into a MK1 engine bay like they were made to match?
I should add, that though I'll do all of the basics, at this stage I don't envisage carrying out any major engine surgery. I realise there are benefits to be had from playing around with the valves, porting, skimming etc to get it revving a little higher but I think that may have to wait for another day, or more accurately another pay day.
I have lots of further questions but I can see this already a very long winded question so I'll leave it there for now.
Sounds like a feck load of messing about when a std 1.8vvti from a mk 2.5 knocks out 143bhp anyway ?
On that subject I'd love someone more technically minded to let me know if that engine will drop straight into a mk1 or what else needs doing ? Mine is starting to smoke alot from cold and the difference in price between a rebuild and just buying another engine is not that massive
On that subject I'd love someone more technically minded to let me know if that engine will drop straight into a mk1 or what else needs doing ? Mine is starting to smoke alot from cold and the difference in price between a rebuild and just buying another engine is not that massive
Mk2.5 engine is the same 1.8 block and basically the same head as Mk1/2.
Mk2 adds a freer flowing head and VICS over the Mk1 and Mk2.5 adds VVT to the intake cam onto that as well as a much better exhaust manifold and higher fuel pressure.
It's easy to swap a Mk2 1.8 into a Mk2. Swapping a Mk2.5 into a Mk1/2 is a little more tricky as the crank/cam sensors are different and you need something to control the VVT.
Fitting an ecu such as MS would solve most of that.
Mk2 adds a freer flowing head and VICS over the Mk1 and Mk2.5 adds VVT to the intake cam onto that as well as a much better exhaust manifold and higher fuel pressure.
It's easy to swap a Mk2 1.8 into a Mk2. Swapping a Mk2.5 into a Mk1/2 is a little more tricky as the crank/cam sensors are different and you need something to control the VVT.
Fitting an ecu such as MS would solve most of that.
Munter said:
If you wanted something a little different you could go rotary....it's been done before (not by me obviously!).
Otherwise I'd say buy rusty heap. Strip and flog the knackered body for scrap. Play with engine and then drop it into a Exocet.
I like the out of the box thinking. I did briefly consider an RX7 but I think I want something a bit more idiot proof and not sure I could live with the fuel consumption. My wife and I are likely to get a fair bit of use out of an MX5 so want to keep running costs reasonable. Otherwise I'd say buy rusty heap. Strip and flog the knackered body for scrap. Play with engine and then drop it into a Exocet.
Hadn't heard of the Exocet, looks good on the few pics I've seen. Alas though, I need something that is more than just a toy.
jamhow79 said:
Sounds like a feck load of messing about when a std 1.8vvti from a mk 2.5 knocks out 143bhp anyway ?
On that subject I'd love someone more technically minded to let me know if that engine will drop straight into a mk1 or what else needs doing ? Mine is starting to smoke alot from cold and the difference in price between a rebuild and just buying another engine is not that massive
Swapping a head over would be no real effort if there were gains to be had. I was really just trying to establish if there were a case for a non-VVT head as that seems to be what many of the really highly strung engines are based on. No idea why. On that subject I'd love someone more technically minded to let me know if that engine will drop straight into a mk1 or what else needs doing ? Mine is starting to smoke alot from cold and the difference in price between a rebuild and just buying another engine is not that massive
MX-5 Lazza said:
Mk2.5 engine is the same 1.8 block and basically the same head as Mk1/2.
Mk2 adds a freer flowing head and VICS over the Mk1 and Mk2.5 adds VVT to the intake cam onto that as well as a much better exhaust manifold and higher fuel pressure.
It's easy to swap a Mk2 1.8 into a Mk2. Swapping a Mk2.5 into a Mk1/2 is a little more tricky as the crank/cam sensors are different and you need something to control the VVT.
Fitting an ecu such as MS would solve most of that.
Cheers. From reading around, I was under the impression that the MK2.5 got a central crank support bearing (I'm guessing) which makes them stronger under extreme load. Is that not the case?Mk2 adds a freer flowing head and VICS over the Mk1 and Mk2.5 adds VVT to the intake cam onto that as well as a much better exhaust manifold and higher fuel pressure.
It's easy to swap a Mk2 1.8 into a Mk2. Swapping a Mk2.5 into a Mk1/2 is a little more tricky as the crank/cam sensors are different and you need something to control the VVT.
Fitting an ecu such as MS would solve most of that.
Sounds a straight forward swap though if I'm using megasquirt.
snotrag said:
Basically that, but it will be expensive for the power gain. Mk2.5,megasquirt, throttlee bodies, and no maf. Plus all usual exhaust etc etc. Maybe 170 hp at the crank if your lucky?
Cheers. Yeah, I'm fully aware this is not the economical route to high power but it is still my preference, I think. Call me nostalgic, but I used to love twin cam fours with a big pair of carbs. I'm hoping the throttle bodies MX5 can give me a bit of that. It's not just about the power for me.In terms of expectations, I actually barely anticipating any increase on stock output. What I'm hoping for is a lovely induction noise and pin sharp throttle response. I'd also like the thing to rev cleanly. My 1.6 always seemed a bit coarse at high revs, like it dodn't really want to be there. To that end I thought I'd pop a lightened flywheel on as well. If I get even 150 bhp I'd be a happy bunny.
If it's to be a VVT engine, I assume there is no benefit/requirement to fart around with verniers?
I thought it was usually more a case of fitting a Mk2 head to a Mk1 block on Mk1s to take advantage of the improved breathing. Not heard of anyone fitting a Mk2 head to a Mk2.5 and I have no idea what the benefit would be other than not having to control the VVT (though it's a very simple system, I believe it just goes to full advance (or is it retard? I can never remember) at certain revs and off again at another higher rev limit). It's just there to boost mid-range torque so I guess the serious tuners aren't interested in it.
Haven't heard about any material changes to the Mk2.5 block. It's quite possible but I always thought the early Mk1 1.8 block was supposed to be the strongest. The MX5 engine was developed from the 323 Turbo engine so is over-engineered fro what it is and all are capable of over 250bhp without any changes to the block. Mine is a stock Mk2.5 block with a SC giving over 240bhp.
As for verniers, as the VVT is basically off at low and high revs then I guess there is still a case for them. How much gain there is to be had from them I have no idea. They do look pretty though
I used to have a 1971 Rover P6 2200TC with twin SU carbs onto which I fitted chrome K&N pancake filters and a large-bore straight-through exhaust with a single mid-exhaust silencer. It sounded superb and went very well. A touch over 160bhp is what the tuner said (no rolling road). It was definitely quicker than a mates Capri 3.0 and the sound was glorious, better than another mates Rover 3.5 SD1. I also had a Cortina 2.0 GT Coupe (2-door in bright orange, same colour the Focus ST was launched with) fitted with a pair of twin Del-orto carbs "borrowed" from Lotus where I worked at the time. A guy in engineering there made a manifold for me as an engineering exercise
Haven't heard about any material changes to the Mk2.5 block. It's quite possible but I always thought the early Mk1 1.8 block was supposed to be the strongest. The MX5 engine was developed from the 323 Turbo engine so is over-engineered fro what it is and all are capable of over 250bhp without any changes to the block. Mine is a stock Mk2.5 block with a SC giving over 240bhp.
As for verniers, as the VVT is basically off at low and high revs then I guess there is still a case for them. How much gain there is to be had from them I have no idea. They do look pretty though
I used to have a 1971 Rover P6 2200TC with twin SU carbs onto which I fitted chrome K&N pancake filters and a large-bore straight-through exhaust with a single mid-exhaust silencer. It sounded superb and went very well. A touch over 160bhp is what the tuner said (no rolling road). It was definitely quicker than a mates Capri 3.0 and the sound was glorious, better than another mates Rover 3.5 SD1. I also had a Cortina 2.0 GT Coupe (2-door in bright orange, same colour the Focus ST was launched with) fitted with a pair of twin Del-orto carbs "borrowed" from Lotus where I worked at the time. A guy in engineering there made a manifold for me as an engineering exercise
Why not go the whole hog?
http://www.youtube.com/watch?feature=player_detail...
I don't think those engines are especially heavy either though you will probably need stiffer front springs.
http://www.youtube.com/watch?feature=player_detail...
I don't think those engines are especially heavy either though you will probably need stiffer front springs.
MX-5 Lazza said:
I thought it was usually more a case of fitting a Mk2 head to a Mk1 block on Mk1s to take advantage of the improved breathing. Not heard of anyone fitting a Mk2 head to a Mk2.5 and I have no idea what the benefit would be other than not having to control the VVT (though it's a very simple system, I believe it just goes to full advance (or is it retard? I can never remember) at certain revs and off again at another higher rev limit). It's just there to boost mid-range torque so I guess the serious tuners aren't interested in it.
Haven't heard about any material changes to the Mk2.5 block. It's quite possible but I always thought the early Mk1 1.8 block was supposed to be the strongest. The MX5 engine was developed from the 323 Turbo engine so is over-engineered fro what it is and all are capable of over 250bhp without any changes to the block. Mine is a stock Mk2.5 block with a SC giving over 240bhp.
As for verniers, as the VVT is basically off at low and high revs then I guess there is still a case for them. How much gain there is to be had from them I have no idea. They do look pretty though
I used to have a 1971 Rover P6 2200TC with twin SU carbs onto which I fitted chrome K&N pancake filters and a large-bore straight-through exhaust with a single mid-exhaust silencer. It sounded superb and went very well. A touch over 160bhp is what the tuner said (no rolling road). It was definitely quicker than a mates Capri 3.0 and the sound was glorious, better than another mates Rover 3.5 SD1. I also had a Cortina 2.0 GT Coupe (2-door in bright orange, same colour the Focus ST was launched with) fitted with a pair of twin Del-orto carbs "borrowed" from Lotus where I worked at the time. A guy in engineering there made a manifold for me as an engineering exercise
Great info thanks and good to find a kindred spirit on the whole twin carb thing Haven't heard about any material changes to the Mk2.5 block. It's quite possible but I always thought the early Mk1 1.8 block was supposed to be the strongest. The MX5 engine was developed from the 323 Turbo engine so is over-engineered fro what it is and all are capable of over 250bhp without any changes to the block. Mine is a stock Mk2.5 block with a SC giving over 240bhp.
As for verniers, as the VVT is basically off at low and high revs then I guess there is still a case for them. How much gain there is to be had from them I have no idea. They do look pretty though
I used to have a 1971 Rover P6 2200TC with twin SU carbs onto which I fitted chrome K&N pancake filters and a large-bore straight-through exhaust with a single mid-exhaust silencer. It sounded superb and went very well. A touch over 160bhp is what the tuner said (no rolling road). It was definitely quicker than a mates Capri 3.0 and the sound was glorious, better than another mates Rover 3.5 SD1. I also had a Cortina 2.0 GT Coupe (2-door in bright orange, same colour the Focus ST was launched with) fitted with a pair of twin Del-orto carbs "borrowed" from Lotus where I worked at the time. A guy in engineering there made a manifold for me as an engineering exercise
CDP said:
Why not go the whole hog?
http://www.youtube.com/watch?feature=player_detail...
I don't think those engines are especially heavy either though you will probably need stiffer front springs.
Nice! Not really my cup of tea but seriously impressive. I'm guessing the bonnet is an unusual shape!http://www.youtube.com/watch?feature=player_detail...
I don't think those engines are especially heavy either though you will probably need stiffer front springs.
MX-5 Lazza said:
I thought it was usually more a case of fitting a Mk2 head to a Mk1 block on Mk1s to take advantage of the improved breathing. Not heard of anyone fitting a Mk2 head to a Mk2.5 and I have no idea what the benefit would be other than not having to control the VVT (though it's a very simple system, I believe it just goes to full advance (or is it retard? I can never remember) at certain revs and off again at another higher rev limit). It's just there to boost mid-range torque so I guess the serious tuners aren't interested in it.
Haven't heard about any material changes to the Mk2.5 block. It's quite possible but I always thought the early Mk1 1.8 block was supposed to be the strongest. The MX5 engine was developed from the 323 Turbo engine so is over-engineered fro what it is and all are capable of over 250bhp without any changes to the block. Mine is a stock Mk2.5 block with a SC giving over 240bhp.
As for verniers, as the VVT is basically off at low and high revs then I guess there is still a case for them. How much gain there is to be had from them I have no idea. They do look pretty though
I used to have a 1971 Rover P6 2200TC with twin SU carbs onto which I fitted chrome K&N pancake filters and a large-bore straight-through exhaust with a single mid-exhaust silencer. It sounded superb and went very well. A touch over 160bhp is what the tuner said (no rolling road). It was definitely quicker than a mates Capri 3.0 and the sound was glorious, better than another mates Rover 3.5 SD1. I also had a Cortina 2.0 GT Coupe (2-door in bright orange, same colour the Focus ST was launched with) fitted with a pair of twin Del-orto carbs "borrowed" from Lotus where I worked at the time. A guy in engineering there made a manifold for me as an engineering exercise
Meant to add the reference to the crank bearing support came from this site. It is american though so maybe slight differences.Haven't heard about any material changes to the Mk2.5 block. It's quite possible but I always thought the early Mk1 1.8 block was supposed to be the strongest. The MX5 engine was developed from the 323 Turbo engine so is over-engineered fro what it is and all are capable of over 250bhp without any changes to the block. Mine is a stock Mk2.5 block with a SC giving over 240bhp.
As for verniers, as the VVT is basically off at low and high revs then I guess there is still a case for them. How much gain there is to be had from them I have no idea. They do look pretty though
I used to have a 1971 Rover P6 2200TC with twin SU carbs onto which I fitted chrome K&N pancake filters and a large-bore straight-through exhaust with a single mid-exhaust silencer. It sounded superb and went very well. A touch over 160bhp is what the tuner said (no rolling road). It was definitely quicker than a mates Capri 3.0 and the sound was glorious, better than another mates Rover 3.5 SD1. I also had a Cortina 2.0 GT Coupe (2-door in bright orange, same colour the Focus ST was launched with) fitted with a pair of twin Del-orto carbs "borrowed" from Lotus where I worked at the time. A guy in engineering there made a manifold for me as an engineering exercise
http://www.liptonius.com/miata/mission/engines_fil...
"One of the unique improvements for 2001 was the addition of a Main Bearing Support Plate (MBSP). Even though the 'B' engine uses 5 mail bearings the crankshaft can still flex quite a bit at higher revs and output levels. Mazda added a MBSP by tying the main caps together bolting it to a thicker stamping if the windage tray."
Gad-Westy said:
Another question. Is the 6 speed box a straight swap and would it be worth going for one or no real benefit?
No real benefit.Here's how the ratios look, both the 4.1 rear end.
It'll mean more shifting about town, but won't make a great deal of difference on more open roads.
The shifter mechanism doesn't feel as good. Not great when you have to use it more often!
Edited by Kozy on Thursday 14th March 12:13
Not sure I agree with that. Mine is 6-speed and the shift is just as good as my old 5-speed Mk1 was (much better in fact between 1st & 2nd). Mated with the longer TorSen dif on the Mk2.5 Sport it's geared for over 150mph in 6th.
For a standard or NA tuned car the shorter closer ratios mean that it's easier to keep the power up. NA tuning usually means a shorter power band and less mid-range so keeping the ratios close can help.
I'm sure I've read that the 6-speed is a bit stronger too.
On my own car, having a supercharger means I have plenty of torque everywhere so to be honest, I could get away with having a 4-speed but I generally just leave it in a higher gear so that negates that.
We could do with some input here from RichyVRLimited, he's the real expert on this subject...
For a standard or NA tuned car the shorter closer ratios mean that it's easier to keep the power up. NA tuning usually means a shorter power band and less mid-range so keeping the ratios close can help.
I'm sure I've read that the 6-speed is a bit stronger too.
On my own car, having a supercharger means I have plenty of torque everywhere so to be honest, I could get away with having a 4-speed but I generally just leave it in a higher gear so that negates that.
We could do with some input here from RichyVRLimited, he's the real expert on this subject...
Edited by MX-5 Lazza on Thursday 14th March 14:33
There is the possibility that the one I drove was a bad example, or maybe I didn't have enough time to get used to it,, but I jumped straight out of it back into mine and going back to the 5 speed I vowed never to go to the effort of doing the swap, as mine felt leagues better.
You're right that with the longer FD, the 6th will be much longer but considering it'll make 1-5 similar to stock, really it seems like a lot of hassle and expense to do the box, diff and FD all to get lower cruising RPM. On a FI car it may pay off if you get to stretch it out on track, but an NA car is unlikely to ever need it the extra range?
Personally, I'd much rather spend the £600 odd quid it would cost me (bit of a guess admittedly) on a set of Jenveys...
You're right that with the longer FD, the 6th will be much longer but considering it'll make 1-5 similar to stock, really it seems like a lot of hassle and expense to do the box, diff and FD all to get lower cruising RPM. On a FI car it may pay off if you get to stretch it out on track, but an NA car is unlikely to ever need it the extra range?
Personally, I'd much rather spend the £600 odd quid it would cost me (bit of a guess admittedly) on a set of Jenveys...
Thanks kozy. The six speed ratios look quite appealing on that chart. If I'm reading it right, with a like for like final drive, I'd get five gears in the same range as the 5 speeder's first four gears, and then a slightly low top gear? So less good for motorway cruising but should be easier to keep the engine on the boil.
Gad-Westy said:
Thanks kozy. The six speed ratios look quite appealing on that chart. If I'm reading it right, with a like for like final drive, I'd get five gears in the same range as the 5 speeder's first four gears, and then a slightly low top gear? So less good for motorway cruising but should be easier to keep the engine on the boil.
Yes pretty much! If you get the longer 3.9 final, they'll look like this:
Probably not enough of a change to warrant the expense though.
Haven't got a chart for the 3.6, but IIRC 1-5 are similar to stock, and you get a nice long 6th.
If you go for it, look into upgrading the shifter bushings, and anything else you can do really.
snotrag said:
Basically that, but it will be expensive for the power gain. Mk2.5,megasquirt, throttlee bodies, and no maf. Plus all usual exhaust etc etc. Maybe 170 hp at the crank if your lucky?
...just out of interst, how expensive do you think?...1.8 throttle bodies are about £700.00, how much into for the rest...Gassing Station | Mazda MX5/Roadster/Miata | Top of Page | What's New | My Stuff