E30 2.9L Stroker ITBs etc build...

[mrlucretius]

Engine Specs

What are the exact specs of your engine: bore, stroke, CR, head, cam

Maybe I am wrong about 10.5:1 CR. From my expert engine mechanic:


Crankshaft - BMW M52 84mm stroke

Connecting rods - BMW M52 135mm (lighter than 135mm M20)

Pistons - 85mm custom Diamond forgings modifed

Cylinder head - BMW M20 885, custom hand ported, Schrick 288 camshaft, new OEM valve springs, Bimmerheads heavy duty rocker arms, all new OEM associated hardware

Compression ratio - Compression ratio has been estimated by the dynamic compression test pressures recorded, but the definitive result is subject to two unknown factors; the custom piston dome cc volume and cylinder head cc volume (depending on how much the head was milled). Utilizing the basic NOT2FAST calculation program, with the test pressures of 185 psi, the result was 12.5:1. However, there are more detailed programs but they require known piston dome cc volume, combustion chamber cc volume and a few other values. Using a more detailed program, with different published piston dome and head cc volumes, I came up with 12.3:1 to 12.8:1.

Engine displacement - Technically, your motor is 2859.9 cc. Just a tick over-square, which is a great place to be.

[2mAn]

Specs:

1989 e30 325is, ~160k miles
m20 stroker 2.9L 10.5:1 CR
...
I'll see if I can get more specific on the stroker details: pistons, crank, etc.

very curious how you got to 10.5:1 and 2.9L

Cool project, just keep dumping money in it and enjoy it. Dont stress about the final BHP #, Im sure its a blast

[digger]

Right now I am going to have to work with the dbilas. This project is over budget by 50% so far and I am feeling broke. :)

What is the chance I can neck down the dbilas trumpets and get more velocity?

I see this is all about gas momentum and friction, and I can see why you like the RHD design.

I wonder how dbilas came up with their design? Aside from being stock-able with the brake booster...

You could do anything really if you wanted….epoxy/sleeve the intake manifold, sleeve the throttle bodies, cut off the dbilas runners on the airbox and fab up something using mandrel bends. You can’t really solve the length issue which is at least half the issue.

Dbilas should have went to down the H27SP route with the longer runners IMO.

If I had only limited time I would do a comparison of my current 45mm Jenvey setup and a 42mm roller barrel setup I have for spare.

For a stock mild cam 2.5 litre engine it seems obvious that 45mm diameter is too large, but is it for a race prepped 84mm stoker engine too ?

Sorry about messing the thread with own agenda... Nice car anyway!

What are the exact specs of your engine: bore, stroke, CR, head, cam, exhaust config (lengths & diameter of primary/ secondary) and ITB (size and overall runner length)?

Ultimately it comes down to the hp the engine makes and rpm that is most important

[nando]

Any dyno evidence about this dBilas/RHD comparison ?

Every single dbilas ITB build I've seen in almost 20 years of E30s has been disappointing. I don't think anyone ever broke 200whp (maybe one guy).

[digger]

That was my post. Same two cars I posted above, but have about 50-70 or so dyno pulls of each, so the ones I posted yesterday may not be the exact ones posted on tech.

Haven't decided yet, but it was a race car and the owner cut the cage out, put an interior in it and is daily driving it on nice days. He is a little apprehensive about even going bigger cam at all.

I agree with Digger. Mid to high 13's under power is where the m20 is happiest.

There was another on a dyno dynamics, a guy from Melbourne iirc.

288 on itbs ms2 is totally daily driveable, stock manifold motronic yeah is much less so

[hasa]

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

If I had only limited time I would do a comparison of my current 45mm Jenvey setup and a 42mm roller barrel setup I have for spare.

For a stock mild cam 2.5 litre engine it seems obvious that 45mm diameter is too large, but is it for a race prepped 84mm stoker engine too ?

Sorry about messing the thread with own agenda... Nice car anyway!

[mrlucretius]

That was my post. Same two cars I posted above, but have about 50-70 or so dyno pulls of each, so the ones I posted yesterday may not be the exact ones posted on tech.


Haven't decided yet, but it was a race car and the owner cut the cage out, put an interior in it and is daily driving it on nice days. He is a little apprehensive about even going bigger cam at all.


I agree with Digger. Mid to high 13's under power is where the m20 is happiest.

So, I am new to the custom ECU / tuning game...

How do I safely increase AFR and avoid predetonation? Maybe it is worth installing a knock sensor + circuit to use manually with headphones during tuning?

And related I have read for spark advance I should just increase timing until torque stops increasing?

To be clear, I am at a mile high, and running 91 octane pump gas...

[mrlucretius]

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.

Right now I am going to have to work with the dbilas. This project is over budget by 50% so far and I am feeling broke. :)

What is the chance I can neck down the dbilas trumpets and get more velocity?

I see this is all about gas momentum and friction, and I can see why you like the RHD design.

I wonder how dbilas came up with their design? Aside from being stock-able with the brake booster...

[mrlucretius]

Specs

I just went through this thread, great stuff. What does your 2.9L setup consist of? Also, that wasted spark setup looks nice.

Specs:

1989 e30 325is, ~160k miles
m20 stroker 2.9L 10.5:1 CR
+1mm intake valves, mild port + polish
dbilas ITB setup with custom cold air intake
long tube IE headers
full custom SS dual 2.25" exhaust
MS2PNP from DIYAutoTune
Innovate LS2 wideband O2
Schrick 288 with adjustable cam sprocket
wasted spark setup - Bosch coil 0221503002 + DIYAutoTune QuadSpark

I'll see if I can get more specific on the stroker details: pistons, crank, etc.

[ForcedFirebird]

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

That was my post. Same two cars I posted above, but have about 50-70 or so dyno pulls of each, so the ones I posted yesterday may not be the exact ones posted on tech.

How come not the 288?

Haven't decided yet, but it was a race car and the owner cut the cage out, put an interior in it and is daily driving it on nice days. He is a little apprehensive about even going bigger cam at all.

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?

I agree with Digger. Mid to high 13's under power is where the m20 is happiest.

[digger]

Low 13s is what seems to work well for me. Enrichment that shows a lean spike gives the best response

[AWDBOB]

I just went through this thread, great stuff. What does your 2.9L setup consist of? Also, that wasted spark setup looks nice.

[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?

[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?

[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.