tveltman

Well, check this out as a means to eliminate turbo lag. Post-cats means lower temps, so the solution seems ideally fitted

http://paultan.org/2006/08/16/how-do...geometry-work/

tveltman

And the turbos can presumably be had from porsche. 100% win

Alan

Hah - check Porsche pricing for those turbos... and based on the sizing (for a Boxer TT) I'd say you'd need 2 of them.. ouch!

For the real deal check out: https://rennlist.com/forums/showthre...eferrerid=6055

Try to ignore the drama* - the llama was all over it - but there is some good real content in there. Folks have done it on 928's and it really works - I have driven behind one such vehicle (sounds interesting).

*as is always the case with SC vs TC threads...

BTW - watch out! - any SC or TC thread is ALWAYS about both regardless how it starts out

Alan

zoltan944

interesting read, from the looks of it I should be waiting for Porken's low budget turbo set up

Iwanna928

My last project was a 95 Thunderbird SC w/ a 5spd. 3.8L supercharged eaton blower. I had rebuilt the whole engine, w/ serious mods...customdouble IC, 60lbs injectors, maf,intake,heads, cam TB etc, etc, etc.....The reason for the 60lbs injectors was the second stage of the project was going to be the addition on a STS remote turbo w/ a blow thru maf into the blower. It's called compound boosting. Sts makes a nice product and it works w/ no lag.....drive one and you will see. I was looking at useing the turbo for the top end where the engine was dieing. Down low it was a beast.

Project ended when someone stole the Thunderbird! That car would surprise a lot of you if you drove it and the whine from the sc was loud at 17lbs.

Check out the Hellion Project. Mustang Cobra, stock bottom end w/ a twin turbo setup was blowing the heads of the block at something like 33lbs. With a compound boost setup the where at 44lbs of boost and holding strong with over 1,000rwhp!

Still thinking about doing it to a 928 but I am looking at a Euro and a US 84 and I love the spyder intake and can't seem to get past taking it off. If I did I would first put a TVS 2.3 blower on it, then forge the motor when I blow it up and eventually look at a remote. Overkill but I like it.

Of course this would be done in stages as I have a buget of about 6k to 8k a year to play with and first I have to find a 928 and sort it out. That will be done by Sept!

I can get the TVS blower for around 1300. The sister company of Eaton, Harrop(Australian company) US national rep is a former ford employee who helped with the SC design! So he will get me a deal on a blower. Hard to pass on.

Stephen

dprantl

Is the TVS the same mounting dimensions as the earlier Eatons?

Dan
'91 928GT S/C 475hp/460lb.ft

Alan

OK so we are officially now in the thread transition phase from TC to TC+SC.. you know what comes next...

Oh well...

Alan

dprantl

Isn't it funny how inevitable that is?

Dan
'91 928GT S/C 475hp/460lb.ft

zoltan944

Happens everytime.
"hey how about some turbo info...."
then
"my brothers stister supercharger....."
"supercharger putting down XXXXXhp..."
"did you check out _____ SC? Turbos suck...."
"waste of time, too much turbo lag...."
"guys not to hijack but I have a SC question..."

Iwanna928

I love turbo's and SC's! It is all good to me. Owned both, like the SC down low and the turbo's when they hit.

As far as the TVS goes, they are very similar and the snout can be gotten at different legnth's. If you would like to pm me I have drawing's of the 1900 and could get them for the 2.3. It is really an awesome blower, much more efficient than the old design.

Back to the Porsche. I will be buying a 84 from a member and would probably SC it if it wasn't for the spyder intake,(I like roots blowers!) so I guess I will turbo this one!

Stephen

tveltman

Actually, if the turbo(s) are mounted rearward, you could probably pick up a diesel Borg Warner VGT turbo (or two) where the exhaust would be less hot. It wouldn't even require the inconel internals on the 997. I don't know if you could find a way to fit 2 turbos towards the back, but it would definitely produce the best results in terms of reduced lag. Of course, one VGT might be enough to do it in the first place, who knows. Maybe in a few months I'll poke around the pick-and-pull junkyard and see if I can find a modern diesel turbo for cheap and play with it. Passenger car diesel turbos are starting to have this VGT geometry, btw, so all I'd need to find is a BW K03/04 VGT or two.

Iwanna928

That sounds interesting! Would love to see how it turns out.

Stephen

entropy_engineering

I don't understand where the turbo lag thoughts came up. If you look at an engine's airflow, before going into boost even, the volume is such that pressurizing the piping along the way is miniscule at best. Transitioning into boost the volume "used" to fill the piping along the is a joke and won't affect lag. The only relavent factor is setting up the compressor and turbine ratios correctly for the desired effect. There is only one downside to boost on a rearmount, sortof. Let me splain lucy.
Turbo's are driven by basicly three things. One the airflow thru the engine pumping out simply is forced thru the turbine which, obviously will spin it up.
Next, is the thermodynamic drive. The air coming in has a higher temperature and pressure than the air exiting the turbine so it will have a somewhat natural drive to pass the airflow thru, particularly if the exhaust is big and open to allow more of a spread. The best exhaust for a turbocharger is no exhaust (well said corky bell). In my experience I prefer the turbocharger near the motor and not after the cats or anything else, but I haven't messed with rearmount setups much. Ofcourse, the rearmounts DO have the advantage of virtually no exhaust after the turbo unit.
Last, when an exhaust valve opens a shockwave blasts out traveling the speed of sound (which varies based on the temperature and density of its conveyance). Think of two people holding out a slinky and pulling back one rung and letting it go. In something like a "log" manifold this energy is lost thru absorption and converted to heat. This is really a shame because a bit of energy is involved. In a header type manifold this is usefull energy to help minimize spool time because the pulses are carried all the way to the turbine blade tips. My problem with a rearmount are that this is hopeless if catalytic converters are involved, plus the fact pressure waves would likely dissipate a bit at a longer distance anyway.
Rear mount would be great for an automatic car because it would go under load and stay there. Many vehicles with manual transmissions boost hundreds of rpm sooner in higher gears because the time they are under load in that gear. Besides, if early boost is such an issue, go get a sound performance spool valve unit that cuts off half of a t4's turbine inlet until boost is sufficient.

Imo000

And how are you plannign on controlling the VGT? It's not as simple as a conventional one with a vastegate.

tveltman

I think that most people's complaint about turbo systems is that they have to "wait" to get their boost -- the throttle response is not as quick as a supercharger would be. When you are screaming along on the highway (or track), that isn't a big deal, since you are well above the necessary RPMs to spool the turbo. In the city, however, depending on the size of the turbo, you may or may not be spooling off the line, unless you wanted to rev it up before taking off. In a manual car, not too much of a problem, but definitely more problematic on an auto. I suggested VGT as a means to get two rather massive turbos which have much less lag owing to their variable aspect ratio. I suggested the B04VG turbo because it will flow something like 28 CFM (forgive me Tuomo), and is rated by Borg Warner for putting out 150 kW each (200 HP). Now, with just a stock engine, there is no way you could realize that much power because you couldnt pressurize it that high without blowing it up, but there are smaller turbos as well. BW had the additional advantage (in my mind) that their variable geometry systems appear to be entirely controlled by air flow through the turbo, so no electronic signal required. I think that everyone who has ever worked on these cars understands the value of simple, mechanical means of controling a feature as opposed to expensive and complicated solid state devices (not that these aren't an incredible advance, but for a DIY one-off, I'll take the simple route anytime). Those were the ideas I came up with after reading the STS site and a little bit about lag. I think they would work, and the turbos could be had relatively easily from a junkyard (or a european parts distributor for new), they would be far cheaper than the 3500 bucks apiece for the gasoline VGT turbos, and fit easily in the framework of a DIY. I will work a little bit more on the design, and if/when I find acceptable turbos, I'll be sure to post pics, etc...