ForcedFirebird's m20 dyno thread.

[ForcedFirebird]

anymore details? to be fair 310bhp on a European dyno is like 200whp everywhere else (excluding dynocom or land and sea/dynomite)

If there were at least some kind of consistency, BHP calcs could work, but a t56 robs a lot more power then a g260 - calculating backward never works. At least this thread is primarily Dynojet, which I have personally found extremely consistent. The race organizations here often will bring a Dynojet out to the track to catch any cheaters in the HP/WT classes - they are usually within 1-2% of the Dyno we have here by the shop.

[hasa]

That was just a random video I saw in a car sales ad. Not mine absolutely. But from my point of view as E30 owner it looked performing very well.

When the tire pressures, roller friction and tie straps are done ok the measurement of driveline losses work ok. But to be honest there are horrible anecdotal examples where the losses are all over the place.

My ex Bosch FLA 203 dyno was reading 211whp / 249bhp for a M20B29 @7000rpm.

[ForcedFirebird]

My ex Bosch FLA 203 dyno was reading 211whp / 249bhp for a M20B29 @7000rpm.

That sounds about spot on with a dynojet. I have been seeing in the 210-220 pretty consistent with stroker builds.

[dvallis]

Here's a new dyno plot for the thread. M20B28 turbo, 10:1 CR JE pistons, wasted spark, Garrett GT3076R ball bearing oil/water 0.63 turbo

Higher CR gives us a low end lift. Garrett gets to full boost 500 RPM sooner than the original PTE. Might upgrade to E85 so we can add more high end timing and lift the torque curve above 5000 RPM.

[ForcedFirebird]

It's amazing that both graphs are basically identical upto 5000rpm.

So the first has
- standalone ecu
- header
- exrtrude hone
- bbtb and fine style inlet
- tighter squish clearance

But the second has a IE 272, is it regrind or Schrick knock off ?

Reading back, I have a gut feeling the breathing mods helped over 5k RPM. Recently had a customer purchase a Spec e30 legal engine. Rules only allow standard rebuild procedures, max .5mm over stock pistons. He put a megasquirt on it, with headers, and decent exhaust. I wasn't there, but Active Auto in Miami dyno tuned it, and it made 179whp peak.

272 cam was new from IE.

I am sad, it's been at least a year since I have personally dyno'd an m20. Have done a few remote tunes, perhaps I should see if I still have the graphs.Last few trips to the local rollers has been an s50, s52, both e36's, and a formula Sport Racer with a 13b rotary.

[ForcedFirebird]

m20b29 I tuned in a "mile high city" Denver, from here in Florida. After the first two pulls, I read the logs and wondered why they didn't open the throttle all the way (80kpa max), then realized that a mile in the air, you have ~20% less pressure lol. This was before and after tune:

[ForcedFirebird]

Higher CR gives us a low end lift.

But, but, but, you are "supposed" to have 8.5:1! lol

Hogwash. The more power your engine makes NA, will only be amplified by a turbo. Your tuning window just gets narrower as the static CR goes up. This is why 80's turbo Dodge, or even the Grand National had 7.5-8:1 SCR. My second turbo build I ever did was 9.4:1. My twin turbo Firebird was 8.8, just like the stock m20. My user name is based on that "Forced (induction) Firebird".

[mikey.antonakakis]

Very nice results on the Denver car! Yep, 80kPa baro is what I see here (now running the MAP Daddy sensor with the additional baro sensor). N/A up here *should* be about 20% less power as a result, although I’ve wondered if you can go more aggressive on timing and get some of that power back? Or are you hitting MBT before knock with a build like that?

Anyway, that 211whp at 80kPa baro should be something like 264whp at sea level… I bet that engine would do good with some boost, I’d love to get more details on the setup if you can share!

[hasa]

Very nice results on the Denver car! Yep, 80kPa baro is what I see here (now running the MAP Daddy sensor with the additional baro sensor). N/A up here *should* be about 20% less power as a result, although I’ve wondered if you can go more aggressive on timing and get some of that power back? Or are you hitting MBT before knock with a build like that?

Anyway, that 211whp at 80kPa baro should be something like 264whp at sea level… I bet that engine would do good with some boost, I’d love to get more details on the setup if you can share!

Dyno software makes normally barometric compensation to sea level pressure. 211whp sounds quite reasonable for a B29 peaking @6000rpm on sea level.

[mikey.antonakakis]

Dyno software makes normally barometric compensation to sea level pressure. 211whp sounds quite reasonable for a B29 peaking @6000rpm on sea level.

Ah, I’ve been wondering about that… philosophically I don’t know how I feel about that, especially for a turbo car. Implying that a turbo car that makes an actual 500whp in Colorado would be fine making 600whp at sea level does not seem realistic. I’ll give the SAE a call and voice my complaints! Lol

[mikey.antonakakis]

A bit of background to explain why I’m not off my rocker:
I used to work as an engineer in passenger vehicle powertrain, and on one test trip this became readily apparent. We tested a 2015ish 328i against the not-yet-released IS200T or whatever they ended up calling it. Both 2L turbos, 8-speed AT, 240hp, etc. On paper they looked identical.

At sea level, they drove very similarly, similar turbo response, butt-dyno power, driveability. But once we got to higher elevations, the Lexus was obviously down on power by a lot, while the BMW seemed mostly unphased other than a slight drop in boost response (it was night and day difference in the Lexus, it was super laggy at elevation). This led to transmission calibration quality issues on the Lexus as it tried to figure out how to optimize gear selection when it was down on torque/power.

The primary reason for this was that BMW just had a much better engine control system and a better turbo (twin scroll I think). Valvetronic with infinitely variable lift that could lift so small they could throttle the engine without a throttle body most of the time, awesome wastegate control, muffler cutouts to reduce post-turbine back pressure, and a turbo that still worked well enough at high altitude to maintain the same MAP as at sea level.

The Lexus simply would overspeed the turbo at high elevation if it tried to maintain the same MAP, so it was down on power.

Hopefully that highlights my aversion to large baro correction on a dyno - would have been fine for the Lexus, but the BMW would not suddenly make 20% more power at sea level than at altitude, because it definitely did not do the opposite.

[digger]

Yes baro corrections for turbo are pretty much nonsense as the engine for the most part “self adjusts/compensates” depending on how it’s been controlled from an absolute pressure perspective . it’s really only good for a NA engines

[ForcedFirebird]

A bit of background to explain why I’m not off my rocker:
I used to work as an engineer in passenger vehicle powertrain, and on one test trip this became readily apparent. We tested a 2015ish 328i against the not-yet-released IS200T or whatever they ended up calling it. Both 2L turbos, 8-speed AT, 240hp, etc. On paper they looked identical..

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.

[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.

[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