m20b32 11.0:1 CR cam selection

[tinkerputzer]

I did, but it runs way better with 24# injectors.

The correct answer is to use injectors sized just right, and 30# aren't it.

Good to know. For op's sake mine runs just fine on 30#r's, but if i was op i'd take your advice.

[LJ851]

The main weakness to overly large injectors is resolution at idle and light throttle. The open times for the injectors are so small that accurate mapping is difficult/not possible and drivability can suffer.

[digger]

lucky we don't need to meet same requirements for emissions etc as the OEM.

i would use 24lb these will be at about 80% on a decent 3.1L M20, a fully built M20 race engine may need bigger though.

[ForcedFirebird]

lucky we don't need to meet same requirements for emissions etc as the OEM.

i would use 24lb these will be at about 80% on a decent 3.1L M20, a fully built M20 race engine may need bigger though.

I didn't see over 80% with green m50 injectors at 223whp as I mentioned earlier in the thread, although, that was on a 413 DME and a 24v. I have used 24# with m1.3 and 8psi turbo'd and didn't run out of injector, didn't end up putting that one on the dyno to verify WHP before the customer sold the car.

[bmwman91]

Interesting discussion regarding the injectors. I too have used all of those calculators and they all come up saying I need way bigger ones than I do. I think that it is because of their assumption about the BSFC input. 0.45-0.50 seems to be way too high as most relatively modern Otto cycle engines seem to be a lot more efficient than that. If I use 0.45 BSFC, it says that I need 32# injectors to make 205bhp in my 2.1L M42 when I do it just fine with 24# ones (80% max DC). To get 24# out of the calculator, I used a BSFC of 0.37, which matches the low-end on Wikipedia (so take it with a grain of salt).

[tinkerputzer]

The main weakness to overly large injectors is resolution at idle and light throttle. The open times for the injectors are so small that accurate mapping is difficult/not possible and drivability can suffer.

I remember reading this when i went megasquirt but this is a good refresher.

Since we are talking about injectors and the online sizing calculators. Aren't most of those calculators based on running full sequential 1 squirt per cycle and aren't m20's that are still running batch fire 2 squirts per cycle?

[digger]

I didn't see over 80% with green m50 injectors at 223whp as I mentioned earlier in the thread, although, that was on a 413 DME and a 24v. I have used 24# with m1.3 and 8psi turbo'd and didn't run out of injector, didn't end up putting that one on the dyno to verify WHP before the customer sold the car.

something doesn't add up. aren't the greentops like 16lb @ 3b?

my M20 was 80% with 24lb and tinkerputzers was 65% at 30lb so these M20 numbers are in agreement since hp is roughly the same.

24/30 is approx same as 65/80

this would put the M50 50% more efficient combustion which isnt very likely.

unless im missing something? your hear the S52 bolton guys going 24lb so

S50B32 uses 31lb when equivalent value at 3b is used (24lb run at 5b)

we should start another thread lol

[Holland]

Keep this thread going, I need M20 build motivation.

[ForcedFirebird]

something doesn't add up. aren't the greentops like 16lb @ 3b?

my M20 was 80% with 24lb and tinkerputzers was 65% at 30lb so these M20 numbers are in agreement since hp is roughly the same.

24/30 is approx same as 65/80

this would put the M50 50% more efficient combustion which isnt very likely.

unless im missing something? your hear the S52 bolton guys going 24lb so

S50B32 uses 31lb when equivalent value at 3b is used (24lb run at 5b)

we should start another thread lol

Could be Motronic 3.x is just more efficient. The m20 fires 3 injectors at at time and has a single coil. Used the green stock m50 injectors and starting with a stock tune, only had to adjust the constants a tiny bit. First pull was dead across at mid 14's afr, made 223whp, adjusted the constants to get a 12.5 afr (endurance race car, didn't want long lean pulls) and the power dropped to just under 220. Could have gotten the power back by adding timing, but the owner was fine with it.

Turbo engines are a different story. 357whp was made from an m20, 15psi and 36lb injectors just a tad over 80%.

We should know the m20 doesn't adhere to that calculator since the Alpina cars used stock 14.5lb injectors.

Think you and I have discussed this before, you using the Alpina cars as reference, and I was hesitant to belive it, but since we have been doing a metric ton of dyno testing/tuning over the last 1.5yrs, tend to believe these motors are more efficient than one would think. Thought about putting all the pulls on one graph just for kicks, but the eta I mentioned earlier had about 100 pulls after all the testing, graph would be quite busy, even with just that one car.

[digger]

Could be Motronic 3.x is just more efficient. The m20 fires 3 injectors at at time and has a single coil. Used the green stock m50 injectors and starting with a stock tune, only had to adjust the constants a tiny bit. First pull was dead across at mid 14's afr, made 223whp, adjusted the constants to get a 12.5 afr (endurance race car, didn't want long lean pulls) and the power dropped to just under 220. Could have gotten the power back by adding timing, but the owner was fine with it.

Turbo engines are a different story. 357whp was made from an m20, 15psi and 36lb injectors just a tad over 80%.

We should know the m20 doesn't adhere to that calculator since the Alpina cars used stock 14.5lb injectors.

Think you and I have discussed this before, you using the Alpina cars as reference, and I was hesitant to belive it, but since we have been doing a metric ton of dyno testing/tuning over the last 1.5yrs, tend to believe these motors are more efficient than one would think. Thought about putting all the pulls on one graph just for kicks, but the eta I mentioned earlier had about 100 pulls after all the testing, graph would be quite busy, even with just that one car.

well the alpina M20 is way more efficient than mine so the batch fire should not be the issue, however mine is set to fire in 3 pairs from my understanding of the setup in my current map. i don't know why it is set to this but it is the base map i started with.

i would say the head porting and chamber-piston combo is important and the more i look at the MM parts the less i like them but that is my opinion. i also wonder about the "newer" injectors and spray patterns and how these compare to the stock ones and if they are any better....

[ForcedFirebird]

They are based on experience. I used Chevy Trailblazer injectors in my old m20 because I had them. Fuel mileage increased and power did slightly. They are a 4 pintle mist design that sprays almost in both directions (around the valve, rather than a squirt gun effect). Not many people would want to swap them in since a connector change is required, but they spray similar to the m50 injectors, but are what 15-20yrs newer? Cold starts (as cold as you can get in Florida lol) was better and the engine seemed to idle smoother. Wasn't the tune, only constants were changed.

What ECU are you using? There are only 2 injector drivers in M 1.3.

[digger]

They are based on experience. I used Chevy Trailblazer injectors in my old m20 because I had them. Fuel mileage increased and power did slightly. They are a 4 pintle mist design that sprays almost in both directions (around the valve, rather than a squirt gun effect). Not many people would want to swap them in since a connector change is required, but they spray similar to the m50 injectors, but are what 15-20yrs newer? Cold starts (as cold as you can get in Florida lol) was better and the engine seemed to idle smoother. Wasn't the tune, only constants were changed.

What ECU are you using? There are only 2 injector drivers in M 1.3.

its weird i used to get 34 mpg on the highway @ 65-70mph when i had a MM cam (now about 28 mpg @65-70mph with a different camshaft) which is more than i ever got stock so economy is pretty good when not leaning on the acc pedal much.

you would need to get two new sets of injectors with different spray patterns to see if there was a pattern best suited and sequential would be ideal. lots of things that could affect it once you start modifying camshaft and cylinder head. probably an expensive exercise

i use a wolf v500 which will handle sequential on an 8 cyl but never got around to set it up with cam sensor etc.

[ForcedFirebird]

How ironic. Have an 86 944 turbo in the shop right now using a Wolf v5. No locals could get the car to start, its running now, but he has 2cyl with very low comp, engine needs to come apart after a short lived idle tuning.

[ForcedFirebird]

Specially seeing it's an Aussie built unit and also originally ran on Motronic.

[digger]

How ironic. Have an 86 944 turbo in the shop right now using a Wolf v5. No locals could get the car to start, its running now, but he has 2cyl with very low comp, engine needs to come apart after a short lived idle tuning.

i would go autronic if had my time again, more tuners available who know the ins and outs of the system.