Turbo Question

[Fabio421]

Is there a problem with feeding a single turbo from two very unequal length "headers"? Specificaly if you were to run a cross over exhaust pipe from one bank over to the turbo that was mounted near the other bank. I know there is supposed to be a benefit to having your exhaust tubes as close to equal length as possible in N/A applications. But could it cause problems with a turbo?

Thanks

[Herr-Kuhn]

This would work, but expect some heat loss in the cross over tube. A lot of people claim twins are not necessary and that you can just rear bumper mount a single and get the same results. Not true. A single front mount with cross over tube would probably work pretty well though.

If you did something like this the exhaust back pressures would not be totally equal, but I don't think it would be a big problem.

Nothing wrong with a proper single setup, just make sure you mount it close enough to the heads to take advantage of all the heat energy in the exhaust. Remember, the 300-400F drop across the turbine wheel is energy that was given up and put into powering the compressor. A lot of poeple think the TC is just a "fan" in the exhaust stream. It is far more than that...it is a gas turbine and works on a pressure and temperature differential. A thermodynamic pump if you will. Both are essential for maximum performance. The sharp and hot pulse energy is essential for maximum kick. If you can keep the pulses in-tact until they reach the turbine wheel, then you have done a super job. Just remember, headers sag and crack and also lose a lot of heat. Designing a TC exhaust manifold system is a complex design and fabrication exercise that will test your patience. Log style manifolds, if designed properly, can nearly match the top end performance of a header and can make boost earlier...it is a better "averaged" manifold that you can live with day to day.

The turbocharged engine is not nearly as sentive to manifold changes as a NA car would be. I've seen terribly crude looking manifolds put out huge power levels.

[rhjames]

what Herr said is, well said.

with turbo's you can put them anywhere, but you lose the benefits of heat from the exhaust.

When I was watching the development of the "Golden Gator" top alcohol dragster (campaigned in the SE in the '70s), they experimented with all sorts of headers and not.

Short headers feeding into twin turbo's then feeding a supercharger (fueled with methanol) produced a spectacular running machine, although not competitive with a nitro powered car.....but they found that keeping the turbo's as close to the exhaust port as possible made the most power.


if you follow Herr's R&D, you will see a very thorough, and well thought out approach to turbo-ing a 928.



regards---rhjames

[Fabio421]

Originally posted by rhjames
what Herr said is, well said.

if you follow Herr's R&D, you will see a very thorough, and well thought out approach to turbo-ing a 928.

regards---rhjames

Oh I know that. I have been a fan of Mr. Kuhn since the days of Goldmember.

I have recently aquired a 78 widebody that I think I am going to try to turbo charge. It is 8.5 to 1 c.r. so it should lend itself to this project. I originaly wanted to run twins but I believe I will have trouble making them both fit. John, I know you sent those old Callaway manifolds to Don B. Maybe he will let me sketch them before he uses them. But a single will fit easier and be cheaper. I could probably minimize the heat losses at the crossover by ceramic coating it don't you think? I have wanted to do this anyway with the plumbing and hot side to keep underhood temps as low as possible. I'm still in the planning stage for now. BTW John, I need to discuss your distributor retard method with you. Maybe at SITM over a beverage.

[Herr-Kuhn]

Go twins...my new manifold style seems to work well. I'll have results in the near future. The retard method is simple and will take you 1/2 an hour to accomplish. Be glad to show you that trick.

[T_MaX]

I remember the Callaway Goldfinger Project!

I never put two and two together till now