Very good possibilities Wolf_Zero!

I have the datalogging for RPM vs. Map and RPM vs. Timing. You'd be very surprised to see that before and after the exhaust, the timing maps are virtually identical. There is no timing change per se [we're talking a half degree here and there], and the trend is the same: -4 degrees at 2k RPM and goes to +9 degrees at 6500 RPM. The boost curve is basically the same shape as the torque curves. It's as if the ECU magically detects the backpressure change and alters the PID and/or the boost per RPM targets. It's very strange. Also, FWIW, the AFR's are virtually identical before and after exhaust. The only change in observable operation seems to be the boost level vs. RPM. I can't see the cam phaser position; that may be the only thing left that we haven't accounted for.

 

Wow, only 9* of timing at 6500? I though it was going to be closer to mid-low teens. Although, now that I think about it the higher compression probably doesn't allow it. If you're saying that the timing is practically identical on the stock and than modified runs I guess that throws the timing theory out of the window ( I was looking for timing changes in the early revs). I'm not surprised that your AFR's are the same. The only thing I can think of right now is the valve lift/timing, however that's generally controlled by rpm/load and in those low rpms it shouldn't be changing much if at all. Can't really think of anything else at the moment that would cause something like this.

Is there any reason why you stopped at ~6500 rpm as well? Was it just that power was dropping off and you didn't want to take it up any higher? You wouldn't happen to have a timing map going all the way to redline either would you? I'm curious to see what kind of advance there is near redline.

 

Maybe they decided that it'll be cool to draw an "M" for "Mini" in the torque curve Sorry....stupid joke

 

Ryephile, any updates to this very interesting thread?

 

Probably not, he sold his car. :(

 

Well damn! Just when it was getting good, to. What is he driving now?

 

Man, I ordered my an Alta turbo back exhaust last monday and it's still not here.....geeez; come on guys.

 

So, I'm only resurrecting this thread because I don't want to start a completely new one on custom exhaust systems...but I have a few questions. So I went to a local speedshop and was talking to the guys about building a custom system and they had a few interesting things to say. Let me say now: this shop specializes in Hondas, so they obviously aren't experts on MINIs, but their shop has produced multiple 450+hp / 10sec cars so I'm willing to place trust in their general car knowledge. My initial plans that I proposed to them were a turboback 3" system, eliminating two cats and including a high-flow cat in the new downpipe (not unlike Ryephile's in this thread).

Their initial thoughts were that they were worried about underhood temps (and this was based off of the anatomy of the exhaust system and underhood setup; not anything they had previously read about our cars being 236134 degrees). They thought with the wiring close to the exhaust manifold and a heat shield already in place that an aftermarket/larger downpipe might create too much heat in that area and increase the risk of fire.

Secondly, they thought that if I did indeed decide to replace the downpipe, that I should eliminate the cat in there, too. But like I said earlier, they thought I should leave it.

Lastly, they said that I probably would have no need to do a 3" system and that 2.5" would probably be sufficient.

What do you guys think about all of this?

 

Well, I have no experience in turbo gassers, but I have a experience with normally aspirated ones, and with turbo diesels.

In diesels, which this engine resembles in its injection and induction setup, bigger exhaust equals quicker spool up, and lower egts. According to this site, the gains of a 3" exhaust may be minimal vs. a 2.5" exhaust in an engine that is somewhat larger than ours (I am assuming a 2.0 impreza motor.)

But, he was speaking about the design of a different engine, with an engine bay that is very different, and turbos with different spools. Maybe a good idea would be a compromise. Perhaps have 3" from the turbo to the first cat, then 2.5" from there back. Having the same amount of air in a larger space should lower the temperature of the air, possibly improving temps at intake, exhaust and under the hood. But, this strategy may not work in this engine, since the ECU may be detecting the quick turbo spool and backing off the boost and causing the "M" in the above graphs. People employ boost foolers on the Cummins diesel to avoid the ECU defueling, but gassers do a lot of different things to control boost, leaning out the mixture does not seem to be one that any sane manufacturer would employ. This ECU is a lot more complex, I am not sure giving it wrong information is a good idea.


That said, I know less than those guys do, and I have not received my MINI yet, so I have not had a good look under the hood. I have seen a few cutaways, though, it looks tight in there.

Are the high flow cats that you guys are talking about going to pass the smog test? Would two?

 

Supersprint has both 60 and 65 mm turbo back systems. I installed 60 mm turbo back. When I asked Supersprints guys why I don`t go with 65 mm, they told me the best setup for a stock MCS is 60 mm but if I had larger turbo, then I should`ve chosen 65 mm. So I don`t understand how people go with 76 mm setup.

 

2.5" is plenty. 3" won't hurt, but is probably overkill. The turbo S engine makes 172 hp. Figure maybe 225 well-modified, 250 with bigger mods. Almost certainly not more than that without a turbo swap. 2.5" is plenty of exhaust piping for 250 crank horsepower. 3" pipe MAY get you a little more output, but only at the top end of that power spectrum. And it adds a lot more noise, not to mention higher weight and cost.

--Dan
Mach V
FastMINI.net

 

Agreed. 2.5" will be fine for many folks out there. Heck, 2.75 would even be a good setup because quite honestly you'll never have to worry about upgrading again even if you go well past the stock turbo or go crazy nuts on reworking the stocker.

I figure anybody looking to go higher DUE TO NEED are going to be doing more than just a TBE in the stock setup. Obviously there's still going to be some "mine's bigger" folks out there.

 

Those that are in the "mines bigger" crowd referenced above, and those that don't mind a hit in lower RPM torque to gain improved exhaust performance at the top end. This would be a track car that lives at higher RPM.

To the comment about larger diameters dropping EGTs, that true, but it's at the price of exhaust velocity. This I'm really familiar with on N/A and blown motors, but am just learing how the turbo interferes with scavaging and the like. Other than making tons of power, the turbo is in just the wrong place for really good exhaust design!

Matt

 

Well I'm thinking about doing the 2.5"--possibly 2.75"--for reasons of cost and weight. My new problem is that I already have a Magnaflow muffler that is 3" IN / dual 2.5" OUT. Do you guys think I should try to sell it and get as much as I can and then buy a new muffler or should I just ghetto-rig it to the 2.5" system with a 2.5-3 flange? Is that even possible or would that be stupid/expensive/bad? Also, anymore feedback on the downpipe situation would be great. Thanks for everyone's help.

 

Should be easy to find an inexpensive 2.5">3.0" adapter online.