E30 2.9L Stroker ITBs etc build...

[mrlucretius]

Yeah 180 x 1.15 drivetrain x 1.20 altitude is about 250hp crank at sea level is what I meant.

I will post a Dyno plot from before I fixed the ignition later. Final Dyno runs will be next weekend hopefully.

I will measure header length too. These are the headers:

http://www.iemotorsport.com/bmw/item/M20STG2.html

Ya I read your stuff about itbs... Sticking with dbilas for now.

What do you think of exhaust design?

Also, can I gain some torque without losing top end by advancing cam?

[mrlucretius]

Dyno Plot with Ignition Missing Issue

So here is the last dyno pull.

This is at a mile high near Denver... So the air is thin 20% or so.

The stock ignition could not drive the high compression motor over 5200rpm or so where is starts missing as the revs grow.

So the weird dips to the right of 5200rpm is caused by that.

Also the car pulls hard to over 7krpm now, but the dyno quit at 6500 due to missing...

New wasted spark ignition is installed and the problem is resolved just need to get back on the dyno for a final tune.

[digger]

Yeah 180 x 1.15 drivetrain x 1.20 altitude is about 250hp crank at sea level is what I meant.

I will post a Dyno plot from before I fixed the ignition later. Final Dyno runs will be next weekend hopefully.

I will measure header length too. These are the headers:

http://www.iemotorsport.com/bmw/item/M20STG2.html

Ya I read your stuff about itbs... Sticking with dbilas for now.

What do you think of exhaust design?

Also, can I gain some torque without losing top end by advancing cam?

To get from rwhp to bhp you need to divide by 0.85 assuming 15% losses. The correction for altitude (pressure) is already done by the dyno automatically.

The exhaust design looks ok, you could get more bottom end with longer collectors but there is no guarantee you wont lose from elsewhere in the power band.

You really need to test on the dyno for cam position,the standard position of 288 will probably be ok.

Be aware that MS is notorious for crank sensor issues so it may not have Been a true ignition coil setup problem

[mrlucretius]

Hey Digger,

You are right. Dyno is corrected for baro. So 211 bhp, seems kind of weak.. Let's see what the final tune shows.

We did have crank sensor issues with the megasquirt early on leading to sync lost errors.

A used and then a new crank sensor later, the sync lost errors are gone, based on logs from the dyno pulls.

The wasted spark definitely fixed the missing issues. Pulls hard and smooth to 7krpm+ now on the road. I was confident it was spark since I could adjust the dwell and duration for the stock coil and move the RPM where the missing occured up and down. And also since we are seeing no more sync errors.

So I need to get back on the dyno and finalize tune and accel enrichment. Should get rolling the last weekend of April...

[efficient]

To be clear, Colorado is a pain in the ass relative to many states regarding emissions.

even california?
you'd fail automatically just opening the hood.

[mrlucretius]

California is the worst right?

I'm from Washington after 25 years no emissions..

Montana no emissions.

Colorado always emissions every 2 or 5 years (older than 32 years).

I stupidly thought all states had no emissions after some reasonable age...

It would have been a real issue if this car did not pass. Still not sure how it passed visual under the hood.

[digger]

Hey Digger,

You are right. Dyno is corrected for baro. So 211 bhp, seems kind of weak... Let's see what the final tune shows.

We did have crank sensor issues with the megasquirt early on leading to sync lost errors.

A used and then a new crank sensor later, the sync lost errors are gone, based on logs from the dyno pulls.

The wasted spark definitely fixed the missing issues. Pulls hard and smooth to 7krpm+ now on the road. I was confident it was spark since I could adjust the dwell and duration for the stock coil and move the RPM where the missing occured up and down. And also since we are seeing no more sync errors.

So I need to get back on the dyno and finalize tune and accel enrichment. Should get rolling the weekend end of April...

Make sense to work with what you have for now and get everything sorted, though a better intake system would get you to your 250bhp thought not as OEM looking.

[mrlucretius]

So Digger,

Recalling reading your latest build thread: you like the rhd itbs primarily because they are smaller diameter and longer runners? Second they are layed out to flow a bit better? This is compared to dbilas itbs?

I think you said rhd is 42mm by 300mm?

I think dbilas is 45mm by (unknown to me right now) length?

(This all off the top of my head)...

[mrlucretius]

The exhaust design looks ok, you could get more bottom end with longer collectors but there is no guarantee you wont lose from elsewhere in the power band.

Regarding exhaust design: I recall you showed moving xpipe further back helped bottom end. I think your xpipe was right near the front of the differential? You showed some harmonic calculations, how can I run your model? What tool did you use?

Also, my car is a bit on the loud side. I am tempted to add resonators. Does this help noise wise and does it rob much hp?

I am thinking move xpipe back, either behind or in front of cat, and putting resonators after the headers in the (now lengthened) dual collector pipe section. Similar to your layout on your build thread. Thoughts?

[ForcedFirebird]

Fun project!

To get from rwhp to bhp you need to divide by 0.85 assuming 15% losses. The correction for altitude (pressure) is already done by the dyno automatically.

The exhaust design looks ok, you could get more bottom end with longer collectors but there is no guarantee you wont lose from elsewhere in the power band.

You really need to test on the dyno for cam position,the standard position of 288 will probably be ok.

Be aware that MS is notorious for crank sensor issues so it may not have Been a true ignition coil setup problem

15% loss is actually on the high side for a manual BMW. More than likely closer to 10 or 12 - but either way, what is at the wheels is more important.



I haven't had any issues with MS and the stock crank sensors, provided the air gap is correct. The factory ECU doesn't seem to care as much as the MS, so when installing MS, I put the sensor as close to the reluctor wheel as possible without touching - many locals are using them in daily driven cars with no problems.



I do agree with you, though, the RHD ITB's would produce more power. Everything I have read about the DBilas, not many were happy with results. Even FPorro (who works here at the shop with me) had DBilas and switched to RHD on his 3.1L m20 and was much happier.

[hasa]

Any dyno evidence about this dBilas/RHD comparison ?

[ForcedFirebird]

Any dyno evidence about this dBilas/RHD comparison ?

Well, you could go an purchase both and let us know. ;)


I have actually dyno'd Extrudabody and RHD on m20's with 272 cams, and the RHD made more power throughout the band. Extrudabody used 45mm throttles like the DBilas, but no air box, just open trumpets...





Here was the same car with RHD after rebuilding the bottom end to a 2.8 (still using a 272 cam)...




As you can see power started falling off at 6500, the car is coming back this summer to install a 284 cam and swapping out the IE valves for SuperTech with the 6mm stems, plus a little more valve seat work with the new cutters I have been using.

[digger]

So Digger,
Recalling reading your latest build thread: you like the rhd itbs primarily because they are smaller diameter and longer runners? Second they are layed out to flow a bit better? This is compared to dbilas itbs?
I think you said rhd is 42mm by 300mm?
I think dbilas is 45mm by (unknown to me right now) length?
(This all off the top of my head)...

Yes there are a number of advantages of the RHD setup as verified by the dyno and really is just fundamental design principles:

- The manifold aligns and mates with the cylinder head ports better I think this helps efficiency at high rpm when air speed gets high as it allows the engine to not nose dive at high rpm where the port goes turbulent.

- The diameter (of the runner overall not just the throttle blades) is correct for the power levels the m20 is capable of so this maximizes VE. Most use 40mm which is a 20% reduction in area.

- The length is suitable for the rpm levels the m20 works at so is in tune, again helping VE. RHD is approx 300mm from the head which is just about the longest that fits with the booster and airbox. The dbilas is around 200-225mm I think so atleast 3” too short

- The runners are straighter so you get less losses

Short plus large diameter runners kill the midrange, and even hurt hp if you go too far in the wrong direction.

If you have larger 45mm diameter runners you can make them longer by 2-3” over and above the RHD length to bring the power and torque back, however on the e30 there isn’t space to do that with a brake booster.

Regarding exhaust design: I recall you showed moving xpipe further back helped bottom end. I think your xpipe was right near the front of the differential? You showed some harmonic calculations, how can I run your model? What tool did you use?
Also, my car is a bit on the loud side. I am tempted to add resonators. Does this help noise wise and does it rob much hp?
I am thinking move xpipe back, either behind or in front of cat, and putting resonators after the headers in the (now lengthened) dual collector pipe section. Similar to your layout on your build thread. Thoughts?

What is the goal for the engine? What rpm range are you trying to maximize?
With your setup it has longer thinner primaries, different larger exhaust cam lobe and different exhaust port so I don’t know that you won’t hurt performance in the midrange or topend by making the change. You’d have to test. It’s not a cheap exercise.

I use ENGMOD4T. Resonators help reduce drone if they are good (decent volume and length).

A large volume long muffler at the back and a smaller one maximized to what space you have near the recess for the factory exhaust near the rear subframe seems to work ok.

Any dyno evidence about this dBilas/RHD comparison ?

On e30tech there was an extrudeabdoy to RHD dyno posted that showed large gains ill see if i can find the image

On the south African forums there was a guy who did a dbilas setup and didn’t make any more power than stock and lost a bunch of torque

In my build thread there is a dyno graph showing RHD compared to a dbilas style setup was worth about 25bhp. I modified the dbilas using smaller throttles and made the runners a bit longer. The dbilas still made less torque almost everywhere and only eclipsed the stock one in a narrow band at the topend.

[digger]

Well, you could go an purchase both and let us know. ;)


I have actually dyno'd Extrudabody and RHD on m20's with 272 cams, and the RHD made more power throughout the band. Extrudabody used 45mm throttles like the DBilas, but no air box, just open trumpets...


[ATTACH]127126[/ATTACH]


Here was the same car with RHD after rebuilding the bottom end to a 2.8 (still using a 272 cam)...


[ATTACH]127127[/ATTACH]

As you can see power started falling off at 6500, the car is coming back this summer to install a 284 cam and swapping out the IE valves for SuperTech with the 6mm stems, plus a little more valve seat work with the new cutters I have been using.

How come not the 288?

[mrlucretius]

M20 afr / knock

Hi guys,

One more question.

How do I pick a safe afr? My current tune is at 12.8 target for high throttle / high rpm. Clearly I have no knock sensor.

Right now I am driving around with acceleration enrichment disabled due to troubleshooting the ignition stuff.

It seems like I get more power when I get tpsdot stepping on the throttle and the thing leans out a bit (seen in Dyno logs) you can feel momentary extra power.

What do your stroker m20 afr tables look like?

I will post my afr table in a bit. Warning: this is an incomplete tune! Not for reference...

Also there are some internet things suggesting people have added knock sensors to m20s anyone have experience, comments?