2.7i build issues- new TB fitted and dyno results, confused.

Post Sun Aug 30, 2009 9:37 pm

I figure I have some sort of problem with my M20B27 with 885 head as it is only putting out 160 hp @ 5200 rpm (est flywheel) but 186 ft.lb @3800/3900 rpm.

So what I am looking for is for someone to post or send by e-mail a dyno plot of an car with the same spec as mine that is known to be performing well. The plot must have a torque curve and an AFR plot. I plan to use (with Goeffbob's help) to figure out where my engine is going wrong.

So the spec that I am ideally looking for;

M20B27 botom end
885 head with stock cam
325i intake manifold, throttle body and injectors
027 M20 AFM
Stock air intake
Motronic 1.3 or 1.1
Stock exhuast manifold and exhaust

If your spec differs slightly, please post but let me know the differences in your engine.

Thanks in advance.

[/i][/b]Edit the rpm at which the peak torque is generated.

Post Sun Aug 30, 2009 10:19 pm

Have a look on http://www.e30tech.com/forum/

Post Sun Aug 30, 2009 10:35 pm

What was the compression on your ETA engine?
Wich exhaust and manifold do you have?

This is actually exactly what I would expect from this setup.

Post Mon Aug 31, 2009 12:24 am

Gunni, the CR is 9.35:1 with the stock eta exhuast manifold (which I think is the same as some of the 325i ones). As the engine is in an E28 (I know this an e30 site but you guy's have a great deal more experience with this engine than anybody else so please bear with me) it still has the standard eta (double down pipes, dual pipe middle section but single pipe rear section) exhuast.

The AFR starts of at 13.3 @1600 rpm and declines steadly to 12.2@4800 rpm, then it drops to 11.5:1 where it stays. This is a WOT run only. On part throttle I don't know what it is doing atm.

Engine spec is M20B27 with 885 head and stock cam. 325i intake manifold, injectors and throttle body. Motronic 1.3 conversion with one of Ants 2.7i chips. The engine was not rebuilt and it has 150000 miles at the time of the run of the RR (I know that's not ideal but my budget does not stretch to ideal unfortunatley). It had only been "finished" 3k miles previously. It's also a manual now but thats unrelated.

The RR was Surry rolling road. These are the rear wheel figures.

Could my issue with the AFR and power be as simple as the exhaust restricting gas flow and therefore causing the ECU to overfuel? I hope so as that is something I was planning on changing in the next month. I suppose to further improve air flow I should be looking at a bbtb I assume.

It is slightly reassuring (from someone who should know) to know that this setup should only deliver what I have got.

The reason why I asked for a dyno plot here is that the U.S spec eta engine all have lower CR's and are therefore different.

Any further assistance would be appreciated.

Post Mon Aug 31, 2009 12:46 am

As the ecu doesn´t measure air flow during WOT , then your air flow is way less then what ever the airflow is supposed to be according to Ant´s chip. meaning you are loosing alot of air flow above your peak torque.

Exhaust restriction can be a problem and is the most likely one.
Do the exhaust first and do another dyno run. But if we assume Ant´s chip has been tuned to about 12.5ish AFR. Then 11.5 is 8.6% less air flow.

8.6% air flow on 160hp is 173hp, wich is like 2+- hp from what I would expect from your setup.
If you look at e30.de site , they talk about a setup just like yours and the number 170hp comes up.

Post Mon Aug 31, 2009 12:53 am

I think the eta exhaust manifold bores are smaller and will be restricting power, no sure on the rest of the exhaust though. I would expect 180bhp minimum because your using a 325i head which makes 170bhp with a longer stroke crank which means power should be higher than a 325i's power output.

Post Mon Aug 31, 2009 1:23 am

He´s lacking in compression and squish. That helps the B25 to do what it does.

Post Mon Aug 31, 2009 10:42 am

Ok that helps. It's good to know that the ECU chip is not suspected, which means it easier to put right without having to travel. So in short to get more out of this engine I will need to get a 6 branch manifold like what Frtiz or hottuning supply, a dual pipe exhaust, a bbtb and maybe do something about the AFM?

After that would skimming the head help in raising the CR and hence high end power or would that do mothing due to the shape of the piston. Maybe I should get that 731 head in the shed rebuilt and put that on instead which was the original plan untill the first one I tried developed problems.

Post Mon Aug 31, 2009 12:22 pm

What you need to concentrate on is what´s clocking up the air flow.
No reason to go buy a 6branch manifold if you have other problems.

Take it one step at a time so that you can see gains from each problem getting fixed.

It could be something as simple as incorrect cam timing, you should take a look at that first of all.

Post Mon Aug 31, 2009 12:47 pm

Gunni wrote:He´s lacking in compression and squish. That helps the B25 to do what it does.

That's why i used the later 320i head

Post Mon Aug 31, 2009 1:09 pm

Surly if the cam timing was out I would have more running issues at idle for example and poor fuel economy. I do not have either or I am mistaken about the effects of poor cam timing. Also as the cylinder face was in good condition (supplied by A-tech from a known good engine), no warpage e.t.c, so it was not skimmed and just fitted (I know this is the cheap way) so how could the timing be out if the belt was fitted properly which I belive it was?

I get what you say about one step at time. I will do that. Thankyou.

Post Mon Aug 31, 2009 1:48 pm

Not that simple. you can easily do the cam timing wrong and get a perfectly fine driving motor.

I´ve tried it

But you should at least check if the timing is right, that way you can be sure that it´s not a problem
remembering that assumption is the mother of all mistakes.

Post Mon Aug 31, 2009 2:39 pm

This any good to you?

Spec is similar,except I used 731 head and have a Miller MAF,chip is Ant's 2.7 with Miller's additions.Engine overfuels a bit(!) over 3000rpm.

Post Mon Aug 31, 2009 2:59 pm

daimlerman wrote:This any good to you?

Spec is similar,except I used 731 head and have a Miller MAF,chip is Ant's 2.7 with Miller's additions.Engine overfuels a bit(!) over 3000rpm.

Malcom whos is Martin Webster? and is that at the wheels?

Post Mon Aug 31, 2009 3:03 pm

That is not at the wheels.

Post Mon Aug 31, 2009 6:59 pm

Well it seems I should have used a 731 head. Not to late I suppose. Thanks for posting it. In fact your build as decribed on the wiki pages is what inspired me originally to do this conversion. Their you only had 178 hp, looks like you have had some improvements since then.

Post Tue Sep 01, 2009 2:55 pm

eta wrote:Well it seems I should have used a 731 head. Not to late I suppose. Thanks for posting it. In fact your build as decribed on the wiki pages is what inspired me originally to do this conversion. Their you only had 178 hp, looks like you have had some improvements since then.

posted the graph from the wrong dyno day!
Take the figures/graph in the wiki article as nearer to the truth!
The plot of the graph is near enough the same,just that this one is slightly higher throughout.
Aussie friend,they struggled with my handwriting...love computers and a key board!
Agree that your issue is the head,885 suits 325 pistons,you need the top of the block machining to restore the comp. ratio and a vernier pulley to restore cam timing as well.
I am about to pull the 2.7 out of it's rusty home and shove it into my project cabbie,I plan to have the head off and have the valve seats cut back to take 325 size valves,I also have a 323 cam squirrelled away....

Then a decent re-map is planned with probably a unichip,was considering Miller's 'WAR' chip,but feel that there is no advantage to me over a unichip.