How good are 'typical' cylinder heads from the factory?
Discussion
Yuck. No torque. It isn't pulse tuning properly. The inlet and exhaust lengths, and/or sizes are not letting the cams work properly which is why it wants to rev so high to try and produce power. With the right exhaust manifold and ITBs there's 20/30 ft lbs and about the same bhp to come if the heads are any good, but then they might not be. Only a proper look would tell.
The head uses the CNC program from 1991 Grp A spec.
The intake is 1991 Grp A tapered 17cm length.
Exhaust manifold is 1990 Grp A homologation part.
Exhaust is 2x 50mm with two large straight through silencers.
Having over layed the curve against the old graph I find it difficult to believe that I have less peak torque than before.
What do you think of the BSFC?
Thanks
Steve
The intake is 1991 Grp A tapered 17cm length.
Exhaust manifold is 1990 Grp A homologation part.
Exhaust is 2x 50mm with two large straight through silencers.
Having over layed the curve against the old graph I find it difficult to believe that I have less peak torque than before.
What do you think of the BSFC?
Thanks
Steve
You can't just use duty cycle and expect to calculate injector flow rate accurately from a nominal flow spec. The opening/closing time is probably knocking quite a bit off the flow you calculate like that. The actual fuel pressure will of course be a factor too.
However even so, assuming a fuel specific gravity of 0.75 I get a BSFC of 0.606 lb/hp/hr and that's not too unusual for a high revving highly tuned engine with corresponding high frictional losses at a full power F/A mixture.
590 x 4 x 0.66 x 60 / 1000 x 0.75 x 2.204 = 154.5 lbs / 255 = 0.606
You certainly wouldn't expect anything like the cruise BSFC at low/medium rpm which could be 0.43 or similar from a stock mildly cammed engine at stoich in case that's what you were thinking.
I suggest you take off your inlet plenum and stick some ram pipes on the stubs and see what happens if any of that is possible or even easy. If that doesn't help it'll be something on the exhaust side.
Ain't quite so simple as people like to think bolting bits together in the hopes of a target bhp number as you're now finding out. You've got the worst of the low rpm tractability losses from the long cams without the top end they should be producing. Peak torque should be coming in way before 6800 rpm but it's the fact that peak torque lb ft has actually dropped that's telling you something is very amiss.
Dunno what size butterflies are in that thing but I'd be wanting 50mm ones ideally to not restrict the top end.
However even so, assuming a fuel specific gravity of 0.75 I get a BSFC of 0.606 lb/hp/hr and that's not too unusual for a high revving highly tuned engine with corresponding high frictional losses at a full power F/A mixture.
590 x 4 x 0.66 x 60 / 1000 x 0.75 x 2.204 = 154.5 lbs / 255 = 0.606
You certainly wouldn't expect anything like the cruise BSFC at low/medium rpm which could be 0.43 or similar from a stock mildly cammed engine at stoich in case that's what you were thinking.
I suggest you take off your inlet plenum and stick some ram pipes on the stubs and see what happens if any of that is possible or even easy. If that doesn't help it'll be something on the exhaust side.
Ain't quite so simple as people like to think bolting bits together in the hopes of a target bhp number as you're now finding out. You've got the worst of the low rpm tractability losses from the long cams without the top end they should be producing. Peak torque should be coming in way before 6800 rpm but it's the fact that peak torque lb ft has actually dropped that's telling you something is very amiss.
Dunno what size butterflies are in that thing but I'd be wanting 50mm ones ideally to not restrict the top end.
48s should be fine to 280/290 bhp so they're certainly not what's holding you back at the moment. I'd spec 50s for 300 bhp though and that's what I'd be aiming for if I built one of those engines.
Back to basics as always. Do a compression test and make sure you have at least 200 psi hot cranking pressure. Ideally a bit more on a 4v. 220 psi would be nice. That will tell you that the CR and the cam duration are not out of synch with each other.
Double check the cam timing. Very retarded cams could give a nasty flat power curve like yours.
Look back at my Saab 2v power curve on page 1. That's got as much torque per litre as yours when a 4v should have at least a 10% advantage in that area straight out of the box. That gives you an idea of how much you're losing somewhere.
Back to basics as always. Do a compression test and make sure you have at least 200 psi hot cranking pressure. Ideally a bit more on a 4v. 220 psi would be nice. That will tell you that the CR and the cam duration are not out of synch with each other.
Double check the cam timing. Very retarded cams could give a nasty flat power curve like yours.
Look back at my Saab 2v power curve on page 1. That's got as much torque per litre as yours when a 4v should have at least a 10% advantage in that area straight out of the box. That gives you an idea of how much you're losing somewhere.
stevesingo said:
I am certain cam timing is good as the mechanism for setting, by way of eccentric dowl bushes, is pretty fool proof.
Are you saying you set the cams up properly with a dial gauge on a lifter and a degree wheel on the crank or did you just assume the new cams would be ground to the same timing marks as stock ones?All done with a dial gauge and degree wheel. What I'm saying is, there is no way they could have moved.
[pic[http://garage.s14power.com/data/533/medium/P1030953.JPG[/pic]
Or Post 370 on here... http://forum.s14power.com/showthread.php?t=2508&am...
Head...
Intake...
Exhaust...
[pic[http://garage.s14power.com/data/533/medium/P1030953.JPG[/pic]
Or Post 370 on here... http://forum.s14power.com/showthread.php?t=2508&am...
Head...
Intake...
Exhaust...
Eewww. That's a very strange exhaust system. I didn't twig before when you said "twin pipe system" because I always think "straight six" when people start talking BMW but of course it's only a four pot. I was expecting two 3 into 1 pipes for the six but this is pots 1 and 4 into one pipe and 2 & 3 into another I'm guessing. I don't see how that can pulse tune properly like a normal length 4 into 1 or a 4 into 2 into 1.
Over 25 or so years of doing this professionally, every time someone has come to me for advice with an engine with supposedly known bits that just doesn't do what it ought to it's always been in the exhaust system.
I had a guy once with one of my big valve Pug 205 8v head and rally cam combos which had sod all torque and had to rev to 8k instead of 7k to go anywhere. Sound familiar? I told him his exhaust system was faulty because everything else I'd either done myself or known what the bits were. He swore blind the exhaust was an OE stock manifold (which I know work very well) and a quality straight through system so he ignored me and ran it for another year. It wasn't until the exhaust came off for some work that he discovered it was a cheap pattern manifold with the pots connected to the wrong pipes! With a 4/2/1 off the shelf Maniflow or similar manifold fitted to the same exhaust system it picked up 20 ft lbs and 10 bhp and dropped the revs back down to the norm I know my head and cam work at.
What you need is a 4/1 or 4/2/1 manifold of normal sort of length with primary pipe I/D of 1.75", 2" I/D secondaries and 2.5" I/D single pipe system. Then it'll all work properly and you can send me lots of money.
Over 25 or so years of doing this professionally, every time someone has come to me for advice with an engine with supposedly known bits that just doesn't do what it ought to it's always been in the exhaust system.
I had a guy once with one of my big valve Pug 205 8v head and rally cam combos which had sod all torque and had to rev to 8k instead of 7k to go anywhere. Sound familiar? I told him his exhaust system was faulty because everything else I'd either done myself or known what the bits were. He swore blind the exhaust was an OE stock manifold (which I know work very well) and a quality straight through system so he ignored me and ran it for another year. It wasn't until the exhaust came off for some work that he discovered it was a cheap pattern manifold with the pots connected to the wrong pipes! With a 4/2/1 off the shelf Maniflow or similar manifold fitted to the same exhaust system it picked up 20 ft lbs and 10 bhp and dropped the revs back down to the norm I know my head and cam work at.
What you need is a 4/1 or 4/2/1 manifold of normal sort of length with primary pipe I/D of 1.75", 2" I/D secondaries and 2.5" I/D single pipe system. Then it'll all work properly and you can send me lots of money.
Ahhh,
Not visible from the pictures is this...
50mm primaries, 55mm secondaries.
Which is joined to this, via the X piece.
The X piece is the 2-1 of the 4-2-1, but BMW decided to split the system again. This is a copy of the stock system with a 5mm increase in diameter. Distance to the centre of the X in the same.
Other engines of similar spec (which show more power on the dyno) use same design with a single silencer.
Thanks for the input, it is really appreciated.
Steve
Not visible from the pictures is this...
50mm primaries, 55mm secondaries.
Which is joined to this, via the X piece.
The X piece is the 2-1 of the 4-2-1, but BMW decided to split the system again. This is a copy of the stock system with a 5mm increase in diameter. Distance to the centre of the X in the same.
Other engines of similar spec (which show more power on the dyno) use same design with a single silencer.
Thanks for the input, it is really appreciated.
Steve
With short primaries and long secondaries it's still completely wrong for a long duration cam and the twin pipe system is just bizarre really. Extra weight and cost and no apparent purpose. Anyway you now know the areas, or combination thereof, the problem lies in and it's up to you to work through them.
Edited by Pumaracing on Friday 19th October 00:48
I had the opportunity to visit another set of rollers that a another E30M3 owner had used earlier in the year. Before I start messing with it and spending money, I wanted to be sure what was being measured was representative, so a back to back with a similar car on the same rollers would confirm/deny the existence of a fundamental issue.
His engine build is the same as mine except his engine has a stock head. Similar compression same cams with his cams timed at 102In/106Ex as opposed to 106/106 for mine.
That is about the ball park I was expecting pre build and confirms that there is nothing disastrous wrong.
When I check the valve clearances I might change the cam timing to 102/102 to see if that helps the midrange.
I accept that the exhaust manifold is probably not ideal in terms of tuned length and if I have the funds in the future I may experiment with a different primary/secondary lengths or a 4-1. There is not much available off the shelf so it would have to be a custom fabrication.
Likewise the intake length could be experimented with, but again this would be custom fabrication.
I haven't done a compression test yet as I have been kind of busy since going on the rollers, but it is planned for as part of an annual health assessment.
Thanks for asking
Steve
His engine build is the same as mine except his engine has a stock head. Similar compression same cams with his cams timed at 102In/106Ex as opposed to 106/106 for mine.
That is about the ball park I was expecting pre build and confirms that there is nothing disastrous wrong.
When I check the valve clearances I might change the cam timing to 102/102 to see if that helps the midrange.
I accept that the exhaust manifold is probably not ideal in terms of tuned length and if I have the funds in the future I may experiment with a different primary/secondary lengths or a 4-1. There is not much available off the shelf so it would have to be a custom fabrication.
Likewise the intake length could be experimented with, but again this would be custom fabrication.
I haven't done a compression test yet as I have been kind of busy since going on the rollers, but it is planned for as part of an annual health assessment.
Thanks for asking
Steve
That's nice to be able to see a back to back on the same rollers against a similar engine and gives you some satisfaction that the head is working. If I were to pick a starting point for cam timing for long duration cams in a 4v engine it would be 105 LCA 3 degrees advanced i.e. 102/108 in/ex.
Slightly advanced nearly always gives better results than straight-up timing and 3 degrees of advance is always my go-to number. Then one just has to pick the LCA. It is of course an irritatingly expensive thing in dyno time to find the optimum on, especially with two cams to juggle.
Slightly advanced nearly always gives better results than straight-up timing and 3 degrees of advance is always my go-to number. Then one just has to pick the LCA. It is of course an irritatingly expensive thing in dyno time to find the optimum on, especially with two cams to juggle.
Thanks for the input.
If I change cam timing I should be able to see on the ECU logging where in the rev range the WB02 has added/removed fuel to compensate for the change in VE. This should indicate the positives/negatives of the timing change if not accurately the magnitude of those +/- areas.
Find where the gains are and go back to the rollers to check how much.
Do you think that is workable?
If I change cam timing I should be able to see on the ECU logging where in the rev range the WB02 has added/removed fuel to compensate for the change in VE. This should indicate the positives/negatives of the timing change if not accurately the magnitude of those +/- areas.
Find where the gains are and go back to the rollers to check how much.
Do you think that is workable?
Dave,
Probably won't be until the new year when the weather is better for doing 3rd gear drags up the bypass.
One thing I will have to be careful of is air temp compensations, so I will have to look as to see what channels to log.
I'm guessing that if I have to add say 2% fuel to maintain the previous Lambda, I will have gained 2% power at that point?
I will also probably pull 2degs of advance just in case I get a big jump in VE somewhere.
Here is the Hp/Tq/AFR graph...
FWIW this was on an inertia dyno, which in it's self brought up some interesting observations about how these different rolling road things work, but that is for another day other than if I were looking for a dyno for tuning it would be a hub dyno.
Steve
Probably won't be until the new year when the weather is better for doing 3rd gear drags up the bypass.
One thing I will have to be careful of is air temp compensations, so I will have to look as to see what channels to log.
I'm guessing that if I have to add say 2% fuel to maintain the previous Lambda, I will have gained 2% power at that point?
I will also probably pull 2degs of advance just in case I get a big jump in VE somewhere.
Here is the Hp/Tq/AFR graph...
FWIW this was on an inertia dyno, which in it's self brought up some interesting observations about how these different rolling road things work, but that is for another day other than if I were looking for a dyno for tuning it would be a hub dyno.
Steve
Edited by stevesingo on Saturday 24th November 20:13
from what I learned by reading this thread I was intrigued to see how good my cyl head is when you posted up the formula I checked a bmw m3 3.2 s50b32 cylinder head which I plan to fit onto my 3.0 engine as the inlet valves are bigger as standard by 1mm.
It has 35mm inlets which equates to 35x35x3.142 divide by 4 x by 12 inlet valves =11542 area
I measured the port to be 27mm so 27x27x3.142 divide by4 x 12=6871
6871/11542=59.5% so it seems its at its max.
It looks to be cnc machined and well finished from the factory very similar to the photo earlier on in the thread.
The exhaust valves are 30.5mm which I think are very big!
A couple of questions:
Will increasing the valve size another 1mm without any other modifications increase the power across the rev range or only its potential to flow more air that is the question?
What else can I check on the head can it be improved?
Its making 300bhp@flywheel and has triple fuel injection throttle bodies so I am trying to work out how to unlock the power from this engine.
It has 35mm inlets which equates to 35x35x3.142 divide by 4 x by 12 inlet valves =11542 area
I measured the port to be 27mm so 27x27x3.142 divide by4 x 12=6871
6871/11542=59.5% so it seems its at its max.
It looks to be cnc machined and well finished from the factory very similar to the photo earlier on in the thread.
The exhaust valves are 30.5mm which I think are very big!
A couple of questions:
Will increasing the valve size another 1mm without any other modifications increase the power across the rev range or only its potential to flow more air that is the question?
What else can I check on the head can it be improved?
Its making 300bhp@flywheel and has triple fuel injection throttle bodies so I am trying to work out how to unlock the power from this engine.
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