ForcedFirebird's m20 dyno thread.

[It's Soda Not Pop]

I, too, like the idea of ITBs, particularly on a high revving engine. I gave up on that though. I estimated the price of a 280hp+ 2.8L ITB build for my car, because I don't want any more than 10lb/hp, and I arrived at well over $5,000 just in the ITBs and head (upgraded valve train and porting).

I've been going back and forth on what I want to do. I was sold on ITBs for last 2 years or so. But the power a turbo can give is hard to pass up. Plus overall it will be cheaper. I can always switch over to ITBs later down the road if I want. Or just buy another E30. I do have C10 that I need to work on as well.

[varg]

I've been wanting ITBs for awhile now, but I miss my old turbo car. So I'm thinking of just refreshing my bottom end and hanging a snail on it. I have (in case you didn't guess by now lol) a seta with a 885 and 284/274 cam.

I, too, like the idea of ITBs, particularly on a high revving engine. I gave up on that though. I estimated the price of a 280hp+ 2.8L ITB build for my car, because I don't want any more than 10lb/hp, and I arrived at well over $5,000 just in the ITBs and head (upgraded valve train and porting).

[turbdan]

Boost has a lot of advantages. Can make a buttload more power than any NA build, with a stock cam, pleasant driveability and good mileage.

Are you already running standalone injection? That removes the main obstacle. If the motor isn't using oil and runs well I wouldn't worry about freshening up either. No need for all the foreplay, just get right in there and boost it.

I've never run a hot NA cam with FI. I did try the catcams mild turbo conversion cam. Not a bad option bit the B25 cam spools earlier and makes more power from the bottom up until about 5k. I don't know which I prefer.

[It's Soda Not Pop]

I've never dyno'd one without a turbo on it. They make good bottom end, similar midrange power and they roll over a little sooner than the B25 does on top. This is to be expected with the same intake manifold and the extra displacement.

With boost and a sufficiently large turbine, they hang onto peak power quite a bit longer. I have a chart somewhere with a GT35R at 1.4 bar. Stock B25 cam, super ETA bottom end, 2.5 head and intake. It may be too soon to try to post pics, I just signed up.

I've been wanting ITBs for awhile now, but I miss my old turbo car. So I'm thinking of just refreshing my bottom end and hanging a snail on it. I have (in case you didn't guess by now lol) a seta with a 885 and 284/274 cam.

[turbdan]

You know what I never see dyno plots of? SETA's with a stock bottom end (seta crank, rods, and domed pistons) and a 885 head with a 272 or 274 cam. I always see the 2.7 with crank, rods, and "i" pistons or a m20 with worked over 731 head. Are the SETA 2.7i conversions that rare? I've never dynoed my car (I would love too). I would really like to see those numbers from a true SETA 2.7i build or one with a Bimmerheads head.

I do know what this forum and the internet claim. I just never see any graphs.

I've never dyno'd one without a turbo on it. They make good bottom end, similar midrange power and they roll over a little sooner than the B25 does on top. This is to be expected with the same intake manifold and the extra displacement.

With boost and a sufficiently large turbine, they hang onto peak power quite a bit longer. I have a chart somewhere with a GT35R at 1.4 bar. Stock B25 cam, super ETA bottom end, 2.5 head and intake. It may be too soon to try to post pics, I just signed up.

[jbontke]

I have heard from folks who have done it that I trust, that they make the same HP as a stock m20b25, with slightly more torque.

Is this just a SETA block swap or is the combination tuned? Where the torque is made is important as well. You may see a max gain of ~15ft lbs at peak, but it may have gained more at a lower RPM.

[AWDBOB]

You know what I never see dyno plots of? SETA's with a stock bottom end (seta crank, rods, and domed pistons) and a 885 head with a 272 or 274 cam. I always see the 2.7 with crank, rods, and "i" pistons or a m20 with worked over 731 head. Are the SETA 2.7i conversions that rare? I've never dynoed my car (I would love too). I would really like to see those numbers from a true SETA 2.7i build or one with a Bimmerheads head.

I do know what this forum and the internet claim. I just never see any graphs.

I've never seen a SETA dyno either. I have heard from folks who have done it that I trust, that they make the same HP as a stock m20b25, with slightly more torque.

[It's Soda Not Pop]

You know what I never see dyno plots of? SETA's with a stock bottom end (seta crank, rods, and domed pistons) and a 885 head with a 272 or 274 cam. I always see the 2.7 with crank, rods, and "i" pistons or a m20 with worked over 731 head. Are the SETA 2.7i conversions that rare? I've never dynoed my car (I would love too). I would really like to see those numbers from a true SETA 2.7i build or one with a Bimmerheads head.

I do know what this forum and the internet claim. I just never see any graphs.

[AWDBOB]

Got some fun M20 dyno stuff to share.

Went back up to Jakes to dyno the 2.7 in my car, but more importantly, to convert my buddy Andrew's car (MT2 from post 105) to Jake's PNP M20 standalone and ITBs.

For reference, Jakes dyno is comprised of a dynojet 248 48" roller powered by 3rd party Norwegian dyno software called "YourDyno".

Andrews car on a regular ole Dynojet (SAE correction) in Oct of 2020 made a best pull of 178/179. See post 105 for that sheet.

On Jakes dyno, Andrews baseline pull on the same setup as before was 167/164, compared to the dynojet best of 178/179 of 10/2020. The weather was great both days (in 10/2020 and on Saturday), so they should be relatively similar simulations, but still so many variables at play, so take it with a grain of salt. The dynojet vs jakes dyno comparison is valuable to me, because when we Dyno'd Linda my old 3.1L M20 on Jake's dyno, the numbers seemed lower than expected.

Andrews car is a 3L M20 comprised of S52 crank/rods with 84mm flat top pistons, 9.3:1. Stock 885 head, IE billet 272 cam, BBTB, stock 320i exhaust with eBay catback.

Andrew's 3L Stock vs Standalone conversion, where it ran out of injector on standalone:

Andrew - Stock vs Standalone by Bobbie Morrone, on Flickr



Andrew's 3L standalone vs RHD 42mm throttles, open trumpets. The car lost some mid range, but really picked up strong up top.

Andrew standalone vs ITBS by Bobbie Morrone, on Flickr





3L ITB open trumpets vs RHD Airbox. RHD airbox lost power up top and didn't gain down below. We were only spinning the car to 6300 on the open trumpet pull, would've made more pulling to 6700 like the pull with the airbox.

with and without airbox by Bobbie Morrone, on Flickr


My 2.7 (325e crank/rods, late model "i" pistons, deck shaved 2mm, unknown aftermarket cam, BBTB, stock exhaust, M50 injectors, MarkD chip) vs Andrews 3L on stock ECU:

Andrew vs Boobie - Stock ECU by Bobbie Morrone, on Flickr





My old 3.1L M20 (same dyno) with heavily ported 731 head with +2mm valves, 10.5 comp, 284/280 cam, stock intake mani, BBTB, Dbilas airbox, IE Long Tube headers vs Andrews 3L on standalone (no ITBS). Notice the mid range torque difference on the 3.1. 3.1 had a better pull that made 188, but this is just the one he had handy to overlay

Andrew Standalone vs Linda by Bobbie Morrone, on Flickr




My 3.1L M20 (same dyno) vs Andrews 3L on standalone WITH ITBS. I think the 3.1 would have some crazy gains with ITBs

Andrew itbs vs Linda by Bobbie Morrone, on Flickr





If he sends me any more overlays from the weekend i'll post them up. I blew up the clutch on my 2.7 first pull, so we didn't get to mess with it at all. I think there was still a lot on the table. Unfortunately i also found out my 2.7 was detonating a ton and I caught it too late and ruined my pistons, sadly. I will either build another 2.7 to get better data or go the 3L route but this time with an 885 head.

Anyways, hope this is enjoyable for some. It's always interesting putting these big stroke M20s on the dyno, as they rarely do what the internet says they will. Small details are so incredibly important when trying to extract big power out of them. I'm just trying to get more actual data out there, since there is so little.

Sucks that there are holes in the data but we only had a day to do all of this so we did the best we could. Really needed 2 days to get it all done. IE, each pull to the same RPM, putting injectors in the stock IM on standalone to see that test through, etc. Oh well, better than nothing!

How much would the 3L gain with a free flowing exhaust? What would my 2.7 have made if it had a free flowing exhaust and standalone? What would a 3L make without crappy flat top lower comp pistons? How would a worked 885 head compare to the worked 731 head in the 3.1L?

Hopefully I'll be able to answer these questions, over time.

[FRODADDY]

Compression ration should be in the realm of 9.5-9.7.

[varg]

What's the resulting compression ratio? Stack height is 0.5mm less than stock, combustion chamber larger, how about the deck height/piston to deck clearance?

[FRODADDY]

I wonder what I will be seeing as soon winter is over and I get it tuned.
My winter's project was the following:

• M52B28 crank
• 276° dbilas cam
• 130mm maxpeedingrods
• Early, catless pistons
• Supertech valves
• ported intake manifold and head
• 3" all the way to the MAF (inclusive widened OEM air box)
• late M30 MAF
• enlarged throttle body
• 19 pounds Ford injectors
• OEM exhaust

I just might have made an mistake in terms of the combustion chamber.
In order to equalize the different chambers I mildened the edge of the squish area.

[82eye]

found it ! i gotta lotta reading to get back here though lol

edit : love the thread. makes me wonder where i'd wind up. would be a dart toss of a guess and i'll probably never really know. be fun to see but i'm sure i might not like it lol.

[ForcedFirebird]

Toyota appears to be twin scroll, they just don't advertise it like BMW. https://www.ebay.com/itm/133654648734:

Next time you’re behind a modern BMW turbo car at a stoplight, take a look into the exhaust tips. Often if they have the OEM exhaust cutout/bypass valves, they’re built into muffler outlet. When the driver pulls away from the light at presumably low to medium pedal, you might see the butterfly valve open briefly. Presumably to reduce backpressure to get the turbo to spool faster.

The flapper has been around since the e36 ;) I opened my shop about the same time e46's ended, so got familiar with them and vacuum leaks straight away. Then started the m54 oil pan gaskets, then, then lol. Still rocking e30's, though. We don't work on much of anything after e46, none after e9x.

That little flapper isn't going to change how quickly the turbo spools, however, with a twin scroll system, there's two ways you can go about spool time.

One is to use the twin scrolls the "old fashioned" way, and pump half your cylinders into each division in the turbine - it appears this is what Toyota did.

Two is to have a control valve on one side of the turbine, but the whole engine feeds the whole inlet. Then in early RPM's, the valve can be closed forcing the entire engine through one division on the turbine. This gets the wheel spinning very quickly, but will also choke the engine prematurely, so as RPM increases, you open the valve until the whole turbine is receiving all the exhaust gasses.

I am not familiar with the inner workings of the n20 manifold, but from the outside it appears it may be the latter.

When I started putting turbos on non-turbo cars many years ago, we would just get whatever turbo we could get our hands on. Many big turbos from diesel tractors work well, but the exhaust sides are huge. Many would just block half the turbine, but then people started playing around and using waste gates and utilizing the second half of the turbine. I seem to remember a company making a t4 "quick spool valve" with a flapper door, but they weren't reliable from what I recall.

EDIT:

https://www.enginebasics.com/Advanced%20Engine%20Tuning/Quick%20Spool%20Valve%20Test.html

and

https://spracingonline.com/products/sp-quick-spool-valve

[mikey.antonakakis]

Crazy how similar they look on paper. The turbos are very close, curb weight is within 100lbs, peak tq and power are almost identical, wow. Amazing that these modern cars put out peak toque almost right off idle.

Yeah, IIRC Lexus was a “normal” turbo, sized small to get good response. BMW was using twin scroll, so less tradeoff (and still able to work at altitude where the Lexus turbo hit its speed limit). BMW definitely had better variable valve stuff, and were doing crazy stuff with it and other engine control systems - for example, at light-to medium throttle pedal tip-in, where you just need a little boost to hit target, the throttle plate would go WOT! Just to get the turbo spooled, then would go to whatever steady-state position worked for them.

Next time you’re behind a modern BMW turbo car at a stoplight, take a look into the exhaust tips. Often if they have the OEM exhaust cutout/bypass valves, they’re built into muffler outlet. When the driver pulls away from the light at presumably low to medium pedal, you might see the butterfly valve open briefly. Presumably to reduce backpressure to get the turbo to spool faster.