Delanoso's 2.9L Build

[Delanoso]

We can take the AFM out of the equation. Mine sucks but the one out of the shop's race car only changed the top end really - it ran to redline better than mine but it didn't make anything like 40whp difference. Out of town next week so we're going to have to wait until the week after to pull covers. Irritating delays.

[digger]

For sure there is the question of why you where told it made xyz hp but realistically it's not a 198 rwhp / 210 rwtq engine with the current spec at least on a dynojet so id not go down the path of swapping bits to try and find it

[Delanoso]

The shop owner was convinced the AFM would make a difference because of idle performance. I'm willing to entertain easy stuff like that if it prevents us from having to take the engine apart again.

What figure do you think is reasonable, specifically after an ECU upgrade with the AFM delete? If I'd gotten 185 from the dyno the other day I might have left well enough alone but 160 is extremely anemic by any standard. Bimmerheads says they built the exact formation I have and it made 200 before tuning. Obviously they're better at it than we are but that's a reference. If a Spec E30 car can make 160/160 and a 2.7i frankenmotor can make 175ish, surely a proper 2.9 can make ~200 without ITBs.

[ForcedFirebird]

Not if your pistons are flat tops....

For example, here's some of my results from the shop using stock intake manifolds:

2.7 stock bottom end with 885 head 272 cam: 135whp
2.7 stock bottom end with 885 head stock cam: 140whp
eta with shaved block and b25 pistons (9.4:1): 180whp (another made 172)
Stock .020" over fresh m20b25 (8.8:1): 160whp
Tired m20b25: 145whp
.020" over m20B28 with full deck height (8.5:1), 272 cam: 167whp
m20b25 12:1 885-compatable pistons, 284 cam: 205whp


Note the first three. The only difference, really is the dome shape of the pistons, and compression. With a max shaved head, the flat pistons still only yield 8.4:1 compression, and the domed pistons make it 9.4:1 (one point of compression isn't going to make 40hp more). Even the stock-stroke 8.8:1 b25 makes more power than the "2.7i" - by 15%! Add that to your numbers, and you would be near 185.

If your pistons have flat tops, I would expect that to cost you a significant amount of power, even with the increases compression.

[Delanoso]

Not if your pistons are flat tops....

If your pistons have flat tops, I would expect that to cost you a significant amount of power, even with the increases compression.

That's what I meant by "proper" 2.9L though. FLat top pistons wouldn't be a properly set up 2.9, right? If I have what I ordered, I have the 84mm crank, 135mm rods, custom domed pistons to make 9.75:1 with some decking that should increase that compression. Even with a mild 272 and good working stock stuff around it, that should be pretty close to 200, wouldn't you think?

I'm really only asking so that I can set my expectations to a reasonable level. It's *not* reasonable to expect 160 just as it's not reasonable to expect 240.

[digger]

The shop owner was convinced the AFM would make a difference because of idle performance. I'm willing to entertain easy stuff like that if it prevents us from having to take the engine apart again.

What figure do you think is reasonable, specifically after an ECU upgrade with the AFM delete? If I'd gotten 185 from the dyno the other day I might have left well enough alone but 160 is extremely anemic by any standard. Bimmerheads says they built the exact formation I have and it made 200 before tuning. Obviously they're better at it than we are but that's a reference. If a Spec E30 car can make 160/160 and a 2.7i frankenmotor can make 175ish, surely a proper 2.9 can make ~200 without ITBs.

I don’t think the shop owner has any credibility going by what you’ve described. When is he going to answer the real questions rather than just stalling with nonsense?

A 2.9L with stock motronic, stock intake, 272 cam is not a 200whp engine 170-180 typically if done well.

A bigger engine doesn’t inherently make more peak power. It tries to move more air which COULD make more power but if it can’t breathe properly it won’t make more peak power.
The power is in the cylinder head, camshaft, intake manifold and combustion dynamics.

the camshaft is fairly small, stock intake and pistons might be suboptimal realstic expectations are not much higer than what you have. i'd guess an easy 10 numbers with a proper tune on a standalone.

You’ve got a ported head who did the work?

That's what I meant by "proper" 2.9L though. Flat top pistons wouldn't be a properly set up 2.9, right? If I have what I ordered, I have the 84mm crank, 135mm rods, custom domed pistons to make 9.75:1 with some decking that should increase that compression. Even with a mild 272 and good working stock stuff around it, that should be pretty close to 200, wouldn't you think?

I'm really only asking so that I can set my expectations to a reasonable level. It's *not* reasonable to expect 160 just as it's not reasonable to expect 240.

Custom domed for 9.75:1 means the amount of cc’s in the dome is adjusted. However what is important is the cc’s are correct the but the shape must also be correct to generate mixture motion through squish action (like the OE pistons). The Ross racing pistons I’ve seen don’t seem to have the OE style dome, they might not be perfectly flat tops but if they dont have the relevant OE features youre giving away some free perfromance

[Delanoso]

Had the car on a lift and pulled a bunch of covers on Thursday. Everything looks correct - clearly a forged crank, M52 rods and custom pistons with evidence of the expected balancing. Cam timing was good as well so we're a little stumped. The only thing that makes sense at this point is that the tune is just shite. I'm ordering a Walboro 255 just to make sure I have the proper fuel volume and we've scheduled a date to put the Megasquirt in. We're going to do it in his shop with his resources. ForcedFirebird, what's the best way for me to get in contact with you? I'm willing to pay for the tune and time you can offer so that I'm certain I've got the right set up.

I don’t think the shop owner has any credibility going by what you’ve described. When is he going to answer the real questions rather than just stalling with nonsense?

Agreed, as far as his credibility, at least in terms of the kind of build I'm doing. He was highly recommended by several locals but I'm pretty sure now that they were part of the SPEC e30 racing crowd. He seems to do pretty well in that niche but what I want is a very different thing. Based on some other interactions, I'm about 100% certain he was lied to at this point. This car never made 198 on any dyno. I talked to Bimmerheads myself and they concurred with you - stock ECU and intake on the 2.9l kit = about 180whp. On the other hand, he gave me shocks and strut inserts off of his shelf and he's spent time and lift capacity in his operating business evaluate my car in detail. Apparently he's bought the parts to build a 2.9 for one of his cars. That doesn't sound like a guy who's trying to bamboozle his customers. The bigger thing for me is that I've wanted to go to Megasquirt form the beginning and he didn't want to.

You’ve got a ported head who did the work?

He has a machinist he works with that does all of his race engines. This machinist has had 885 heads on a flow bench for years with good results and there's also dyno proof on that work. The clubs they race in require dyno results to start the season as well as to validate podium positions in all classes. I understand that it's had a three angle valve job as well as some gasket matching and a few other things. I can't remember where in the head but he talked about increasing velocity and some dimpling done to create some turbulence. I get the theory and it seems to line up with what I read in what ForcedFIrebird posts. I'd have to have John's work and the head off my car next to each other to know any kind of difference though.

Custom domed for 9.75:1 means the amount of cc’s in the dome is adjusted. However what is important is the cc’s are correct the but the shape must also be correct to generate mixture motion through squish action (like the OE pistons). The Ross racing pistons I’ve seen don’t seem to have the OE style dome, they might not be perfectly flat tops but if they dont have the relevant OE features youre giving away some free perfromance.

We're trying to get pictures of how the piston tops should look. Bimmerheads insists they're good pistons and they insist they've made well over 200hp on them. Whatever the case, I'm not terribly concerned that they aren't the #1 most perfect option. I'm not trying to squeeze every last horse out of the build. Clearly, what I have should be better than 160, specifically with the stand alone ECU. If it doesn't make 200hp I won't cry, but I do want to understand why it doesn't and what I should expect from it. I think I'm getting there.

[e30sh]

Look for an "84" stroke mark on the crank. M20's have 75 or 81 on them...I assume the 2.8's have them as well. Someone chime in if they know for sure.

[digger]

The pistons are not the root cause even if they are not ideal. I’m sure you can make well over 200 with those pistons if the rest of the engine is built accordingly.

I think Ive said before I’d just get MS pnp and a proper tune and it will be what it will be as there is nothing to suggest you didn’t get the parts you requested. Sure try a chip from FF or something but I don’t see it being a silver bullet.

The above will reveal the quality ( or not ) of the head work (I have my doubts ) as well the overall combination of parts. then you can learn and go from there like I did when I built my 3.1 after being disappointed given the $$$ outlay

[Delanoso]

I think Ive said before I’d just get MS pnp and a proper tune and it will be what it will be

This is where I am. We're installing the MS and I'm hoping FF's tune will clear up the main issues I have. I'd disagree though, that there's nothing to suggest I didn't get the parts I requested. 160whp is significantly below anyone's estimate based on the parts we used so I didn't get something I paid for, which means it was worth it to verify.

[ForcedFirebird]

If you think it's the tune, just stick a stock ECU and injectors in it and note any changes. The stock ECU ran our car no problem, it was just down about 8whp from modified mapping. If the stock ECU is still lacking, then there may be a mechanical issue.

[ForcedFirebird]

Look for an "84" stroke mark on the crank. M20's have 75 or 81 on them...I assume the 2.8's have them as well. Someone chime in if they know for sure.

84mm and more do not. Easy way to spot a 75/81mm, though. For the larger cranks, you must use the casting numbers for identification:

https://www.r3vlimited.com/board/for...nd-2-8l-cranks

[Delanoso]

OK, so now just feel dumb because I can't make sense out of your the stock ECU suggestion. 8whp down from modified mapping meaning a remapped Motronic? Which would mean I'd see an increase from what I have now?

[ForcedFirebird]

The stock ECU with the 2.7 made something like 164whp and went up to 172 with a custom chip. So, the stock ECU with stock injectors should run your car at minimum, and probably won't be far off from adding a custom chip. As digger said, doubt the tune will be the magic bullet, unless the chip you have is really botched. Before spending any money, put the stock stuff in and see if any changes.

[e30sh]

Have we confirmed that it is an 84 mm crank? The balancing pads on those rods look huge compared to the M 42 world from which I come.