nine-44

The stock K26#6 will stay in the stock location, the primary Garrett T-25 VNT will be placed as a Callaway 944. In reality, I'm keeping the stock configuration and adding a similar to the Callaway setup and both feeding into the engine, separate intercoolers, the Impco style changover valve used on the 959, with an exhaust brake to force exhaust flow to the primary turbo. The control electronics will actually be simple but I'm not big on building electronic devices so that may be tricky. I may just utilize a couple electronic boost controllers to control changover to the secondary turbo.

theedge

This is something ive been dreaming of doing sometime WAY down the road.

Now IIRC the VNT turbos have longevity issues when run on gasoline engine? Something about the "dirtier" exhaust, more particles compared to deisel where they are normally used. Have you read anything about this?

nine-44

I've read that the VNTs will suit up and stick when you don't drive them hard(ie. not into boost) and I've read that they adjust the vane so much that it's almost impossible for them to suit up and stick. We'll see I guess. I hope to keep the A/F ratio in check close enough that it won't burn too dirty anyway, efficiency equals power and that's the plan. In stock form I'm sure they run a little rich for margian of safety as with most boosted factory cars. I'm thinking that standalone may be the way to go, I'm not sure if it's in the budget right off the bat tho.

Robby

I don't know much about the technical aspects here, but, a K26, even a #8, will NOT hold a full bar of boost ALL the way to redline, from what many have told me- a K27, however, can, &, is supposed to be just about as easy to install, etc, as a K26- please someone correct me if I'm wrong, but, it just seems to me that if you're going for a twin turbo set-up, that, you may as well make the large one a little larger than a normal turbo- otherwise, you can much more easily scrap the twin turbo idea & get a K26 # 6 & get FULL boost well before 3000rpms w/wastegate mods, chips, etc... hell, the STOCK NORMAL 951 hit 238TQ @ 3500rpms & 217HP @ 5800rpms- the Turbo w/K26 #8 put out 258TQ @ 4000rpms & 247HP @ 6000rpms... Danno has tuned a FEW 951's to get FULL BOOST by 3000rpms w/a K27#8- that's why he advocates the #8 over the #6, as it gives a little more overall & really doesnt take much longer to spool, IF tuned correctly- his all chip tuning anyway, from what I understand & he could burn your chips quite easily... Tony G is big on the K27#6, &, has been very successful, although the dyno's Danno has sent me, have been much more impressive using the #8 & w/little, or NO low end loss... Just food for thought.... In any event, while this may not be the greatest acheivment from a performance perspective, &, may not be 100% necccessary, I DO admire the thought & the uniqueness of it... HELL, people have twin turboed the 928 FFS.... why not the 944? IF ANYTHING, the 944 needs a TT MUCH more than the 928 w/it's big V8....

Robby

Hey, I'm curious... how much weight will this add, overall, AND, how much more would the EXTRA turbo (for TT purposes) add over a single turbo? I'm thinking close to 50lbs & 25lbs more for TT than ST....? The extra IC, etc....? Possibly not quite that much as you don't have room to install too big of parts in there- where is the extra IC going to go anyway?

The Supra TT- is it sequential? I know the RX7TT, 300ZXTT, & 3000GTVR4 were all sequential, but, a friend recently told me the Supra was NOT sequential... anyone care to tell me the various types of TT set-ups? I don't know the name for any other than sequential & the only other way I can think of that a TT would work is BOTH together... I know that most Supra tuners go single turbo for larger #'s, although I've read that above ~900HP or so, they go BACK to TT's... Also- would the turbo set-ups for the supra TT weigh much more than what one would use for our cars? I'm wondering how the Supras end up weighing SO MUCH for such small cars- ~3650lbs vs 3150lbs for Turbo S- that's 500lbs for such a similar sized car... Audi S4s are another one- I'm wondering if going to single turbo for such cars helps much...? I mean, it makes sense for our cars, but, the newer cars have much more technology & wider TQ bands, etc... so, are probably not in as dire need for the extra turbo. The RX7 probably NEEDS a TT b/c of it's 1.3L displacement... Not sure at all about the 300ZX &/or 3000GTVR4, OR, the new Volvo S60R w/it's TT 5cyl- I THINK it's sequential too(?)... anyway, just curious....

Matt H

#1 the lag in a 944 Turbo is not horrible. Car makes full boost by 3K RPMs. When you put the dynos back to back with an NA, it makes as much power all over as the NA does. I have overlayed the charts and we are talking a difference of like 100RPMs.

#2 conceptually, I dont disagree. In practice the much more reasonable way to do this is to eliminate the real problem, the displacement. Same results (actually, probably better), much more user friendly and the added benefit of torque.

Stock K26-6 is out of its effeciency range at the 18psi range. At that point it is nothing more than a blowdryer. Additionally, you wont gain HP at 19-20-21 but you might gain some mid range torque (until the compressor fails).

Yes, it will but generally not with a 20 year old WG.

Non sequential because it has two cylinder banks and makes about 100X more sense.

Only to go to two of the largest turbos you can buy. Single turbo is the way to go. I have done about 5 conversions on RX7s and in college I did I conversion on a 300ZX.

It was done to correct the single biggest problem with small displacement engines. NO TORQUE.

Just some thoughts.

You are going to need a very small turbo for the first turbo, it needs to spool almost immediately and doesnt need to hold more than 10psi (probably more like 6). why not just use a Hitachi IH-6? It fits in the location, is internally WGed, can be had cheap and actually provided most of what you are looking for. Maybe an HT10B (for a GPZ750).

How are you going to control the fuel? The first turbo will require more fuel, when it trims the second turbo will require even more fuel. You will need a multi map setup (standalone or similar).

I know you are one who prefers the unconventional but I have to wonder if you couldnt achieve better results with a 3.0L and get exactly what you are looking for.

You will never make 350-500 with a K26-6, the compressor just cannot flow enough. Budget a much larger secondary turbo (really large like GT35-GT40) depending on your real output goal. If it is 350 then go to a GT25/GT30 or T04E, if it is 500 then I dont think you will have enough turbo until you are at the GT35 stage. BTW, at somepoint with the Garretts you will need a custom intake as they wont fit under the stock one. Any real Garrett is going to require a custom DP and the crossover to be cut/rewelded. T04Es are available with a replica K26 #8 and #10 hotside.
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streckfu's

I love it! How fast was that little bugger?

Chris_924s

It could pull wheelies for some distance..
Dubbed "Torquey, the wonder mower" It served a dual purpose- entertainment and mosquito eradication!

Andy- I'm not surprised, If anyone can accomplish this- you sure can.

Darius Juca

Matt,

I think andy is dead on in his thinking. He will eliminate two great problems that haunt all Single Turbo cars. The first is horrible lag that is apparent even in a stock 951 and that only increases with a larger single turbo.The second is a twin turbo will make his car more streetable and also give him greater throttle response.
some's words but I disagree a bit


Turbo lag is imposible to eliminate only reduce......the second thing is that the system you are trying to develop is too complex to be efficient with a 2.5.....maybe a 3 but even then....before addressing the engine we should go to the gearing and tranny strenght...higher revving heads ligher internals should help you stay in the right rpm range for those tight AutoX tracks you speak of...
But hey should be intersting seeing your complex exhaust,header,crossover.turbine pipe setup...and where you'll put it....and how to manage the heat...But looks like you like to think....

Rock

All I know is... shocks are being ordered in 3 days! Konis all around baby woo hoo!

BTW. If you pull this off, its gonna be pretty cool. I also have no clue as to what youre doing because man, im just a kid, but it sounds neat to say you have a twin turbo 944

Porsche-O-Phile

You can eliminate turbo lag by force-spooling the turbo at even low RPMS, but this is (1) easier said than done and (2) likely to have you replacing turbos at a furious pace!

Riff

First off, I am by no means any form of turbo kowledge base. The only Turbo car I own is the S6 and I know far too little about how it works. That being said, if we are really thinking out of the box, why not go with a supercharger (like the SFR one) in place of the AC and save the serious fabrication on the exhaust side. Would you be able to plumb the intake so both feed into the same IC?? Like I said, this is purely for conjecture. I mean if the goal is immediate throttle resonse, why have a small turbo in the first place. Heck Lancia pulled it off....

Steve PH

Have you considered running a supercharger as stage one of the process in place of the small turbo ? This idea was used briefly but successfully by the Lancia rally team (in the Delta s4) back in the eighties group B era. Basically they ran a supercharger at lower rpm which then shut off and a turbo charger took over. This meant a top end of 5-600 bhp from a 2ltr engine and no lag !

Heres some dead easy do it your self diagrams !





Sorry no hamsters!

Darius Juca

It was innovative but too complex...

J Chen

I'm running a GT25TO4S. Full boost 1.2bar at 3300 rpm & it's
with a reliaboost. Add an EBC boost build up should be even faster.
If you're on a buget may I suggests a K27/6 but relocate the turbo
to the exhaust manifold side. Do not under estimate the benefit of
this. In fact this is on my next to mod list. The other option is to go
supercharging. Look into the Rotrex supercharger, it offers the best
of both worlds. Sequential turbo in theory sounds good but in reality
but does not work out so well unless you adopt the Lancia Intergrale
set up. Positive displacement supercharger for the bottom with turbo
for the top but this is for big hp application. For DE, a supercharge
engine making 300-330 rwhp is more than enough. It's low end
torque that wins the day.