My E30 M20 turbo writeup (lots of pics)

[ryan_george]

No updates really. Car projects have been put on the back-burner, but I'm getting it out of hibernation mode this week hopefully. Still haven't got around to getting on a dyno, either. Anyone know of a good one in the area to spend a few hours tuning?

[InfiniteDice]

I like the heat shield idea. Good job!

One problem you might have is with the exhaust. Seems like it could hit if you are lowered. I've had to have mine re-adjusted and welded up higher already, as I was clipping everying with my resonator. You don't have a resonator so maybe you'll be alright.

My old 2.7i had no resonator and on long drives I'd be deaf. This time I put a nice resonator on and it sounds nice out the back but you don't need to scrape your eardrums off the floor with a spatula afterwards.

[ryan_george]

Originally Posted by InfiniteDice

I like the heat shield idea. Good job!

One problem you might have is with the exhaust. Seems like it could hit if you are lowered. I've had to have mine re-adjusted and welded up higher already, as I was clipping everying with my resonator.

The car is slightly lowered and I have never had an issue. The only time I've hit bottom is going to the cottage on an extremely bumpy and unmaintained road.

[traffik]

Hey very nice build, very clean and almost looking stock like. Have you tuned this car yet? how mush boost are you running? If I can give you a little advice, you might run into boost drop off problems with the way you have the wastegate setup. The angle of the wastegate will cause more exhaust gasses to bypass the turbo then normal. A wastegate should be plummed in horizontally not vertically. This is just food for thought. But i like your setup~!

[ryan_george]

Originally Posted by traffik

Hey very nice build, very clean and almost looking stock like. Have you tuned this car yet? how mush boost are you running? If I can give you a little advice, you might run into boost drop off problems with the way you have the wastegate setup. The angle of the wastegate will cause more exhaust gasses to bypass the turbo then normal. A wastegate should be plummed in horizontally not vertically. This is just food for thought. But i like your setup~!

It's 95% tuned, like I mentioned before, it hasn't seen a dyno yet. Just street tuning.

Boost is set to 15psi and it holds there very strong. I'm not sure I understand your concerns about the wastegate. Care to elaborate?

[Bullet Ride]

I believe he's saying that the runner for the waste gate should enter the manifold at more of an angle wrt the exhaust flow so that the exit path is not too direct because in certain circumstances it will cause the boost to drop when the wastegate opens until the system can catch up. Obviously for your current set-up it's not an issue.

[traffik]

Originally Posted by Bullet Ride

I believe he's saying that the runner for the waste gate should enter the manifold at more of an angle wrt the exhaust flow so that the exit path is not too direct because in certain circumstances it will cause the boost to drop when the wastegate opens until the system can catch up. Obviously for your current set-up it's not an issue.

Yes Bullet ride, That is absolutely correct, A wastegate is used to control boost pressure in turbocharged engines. The waste gate is a valve that bypasses exhaust gas around the turbine wheel of the turbocharger. It is the flow of exhaust gas that causes the turbo to spin which produces boost pressure. In a simplified view, the more exhaust gas the higher the boost pressure. The waste gate opens to vary the amount of exhaust gas that reaches the turbo, which controls the turbo speed and hence the boost pressure. If the wastegate is in the direct path of the exhaust flow then it will possably allow less exhaust gasses into the turbo and more out of the waste gate, which will cause the boost to drop off after the wastegate opens fully. I hope this helps.

[everlast]

Not that I know any better, but if that happened wouldn't the signal to the WG drop, causing it to partially close thus causing boost to build back up again and finally reach an equilibrium?

[ryan_george]

Originally Posted by traffik

Yes Bullet ride, That is absolutely correct, A wastegate is used to control boost pressure in turbocharged engines. The waste gate is a valve that bypasses exhaust gas around the turbine wheel of the turbocharger. It is the flow of exhaust gas that causes the turbo to spin which produces boost pressure. In a simplified view, the more exhaust gas the higher the boost pressure. The waste gate opens to vary the amount of exhaust gas that reaches the turbo, which controls the turbo speed and hence the boost pressure. If the wastegate is in the direct path of the exhaust flow then it will possably allow less exhaust gasses into the turbo and more out of the waste gate, which will cause the boost to drop off after the wastegate opens fully. I hope this helps.

But on the other hand, you want a very clean path to the wastegate to prevent over boosting. And the wastegate (at least this one) isn't like an on/off switch. As the boost level is approached it will start to crack open and slightly bleed off pressure. As more boost continues to build it will open further, etc etc. I understand your concern but this is a fairly small wastegate and it's not an issue at all for this application.

Originally Posted by everlast

Not that I know any better, but if that happened wouldn't the signal to the WG drop, causing it to partially close thus causing boost to build back up again and finally reach an equilibrium?

My thoughts as well

[everlast]

Yeah, it's been my understanding that you want to allow the WG gasses the best chance of passing through the WG.

Of course, taken to the extreme this would affect overall turbo efficiency.

That said, my WG at a 90* angle from the turbo inlet. Does seem to work well.

[traffik]

Originally Posted by everlast

Not that I know any better, but if that happened wouldn't the signal to the WG drop, causing it to partially close thus causing boost to build back up again and finally reach an equilibrium?

No, It would actually cause boost spike at higher RPM's and or more strain on the motor. I built a nissan 240 for a customer with a RB25 skyline engine and he brought me a manifold that had the same style wastegate design as you made yours. after everything was all together and we were tuning the car on the dyno, everytime we would hit boost it would creep and then drop off after reaching full boost 25psi. took a while to figure it out, but after pressure testing for leaks and changing the wastegate, it still did the same thing. so i desided to take the manifold off cut the wastegate pipe and redesign it. installed the first wastegate tial 44mm and boost no longer creeped or dropped off. it would just go from 0psi straight to 25psi with out a pause. Like i said just food for thought! i only give my input on personal experience.

[everlast]

Either I'm not understanding, or this doesn't make sense. I don't see how MORE flow to the WG would cause boost spike or strain on the motor.

But, I'm no expert.