What's Your Boost Setup & Curve

[JM2327]

What’s your forced induction set up, boost curve and how do you like it. Mine is 3.0 liter w/ twin K24 18G turbos. Comp. Ratio 8.9:1 RPM/BOOST/ : 3K/1.6, 4K/3.5,5K/9.3,6K/15.1,6.6K/19.2. This set up works for me because I think it’s easier on everything and fast 60-130 which is my driving style. Maybe a shot of NOS later for down low.

[quattrorunner]

swap out those turbos.

[JM2327]

Well taken! Any suggestions?

[quattrorunner]

I don't know much about the k series little turbos but I think there is a k16? I'm sure you could get 19 psi but sooner. 3.0 is smaller than the 3.6 the k24 was designed for. I have a 3.0 930 and use a single gt30r. My aspect ratio is the .82 but I want to swap to the .63 so I get boost quicker. I see .8 bar by 3200rpm and it holds all the way to 6000rpm where my cams are done. if I wanted to raise the boost, this turbo is good for 525hp.

[quattrorunner]

I'd like to see your intercooler.

[copbait73]

OK, you're saying 19.2psi with a fixed compression of 8.9:1?
When you rebuild your engine use a pair of K16s.

[RarlyL8]

We need pictures of that engine!
K16 should be a better fit for 3.0L displacement.
If I were to "map" boost I would assure full boost was available in the meat of the torque curve and drop it off a touch after 6000rpm. There is no advantage in having twin turbos if early spool and torque are missing.
The figures you quote should be a time bomb on pump gas. Is some info missing? Engine management system? Octane enhancers?

[JM2327]

Originally Posted by quattrorunner

I don't know much about the k series little turbos but I think there is a k16? I'm sure you could get 19 psi but sooner. 3.0 is smaller than the 3.6 the k24 was designed for. I have a 3.0 930 and use a single gt30r. My aspect ratio is the .82 but I want to swap to the .63 so I get boost quicker. I see .8 bar by 3200rpm and it holds all the way to 6000rpm where my cams are done. if I wanted to raise the boost, this turbo is good for 525hp.

K24 18G is a modified GT2 turbo with Mitsubishi 18G compressor wheel and is a popular upgrade to the 996tt stock turbo. The K16 could be a very good and better fit but may be somewhat limitng at 525HP. The K24 has a large 1.0 A/R. I knew going in the turbo was large for my engine but being a hand-me-down from my son modified 996tt I thought I would give them a try. Checking the stock K24 turbo map at the pressure ratio I was looking for it was right in the sweet spot. It is very efficient at 19psi and that coupled with max boost being above max torque lets the engine live better at 8.9:1 CR. The car runs like a stock 930 on steroids with less lag and while not ideal I must say there is a fun factor in that. Like that big flat curve from 3K.

[JM2327]

Originally Posted by quattrorunner

I'd like to see your intercooler.

Here's the intercooler.

[JM2327]

Originally Posted by RarlyL8

We need pictures of that engine!
K16 should be a better fit for 3.0L displacement.
If I were to "map" boost I would assure full boost was available in the meat of the torque curve and drop it off a touch after 6000rpm. There is no advantage in having twin turbos if early spool and torque are missing.
The figures you quote should be a time bomb on pump gas. Is some info missing? Engine management system? Octane enhancers?

I totally agree with you and like your mapping plan. But if we think out of the box for a minute the top end power of the K24 18G set up is great and efficient. I don’t think you can beat it up top The K16 being smaller will probably create a much more heat up top at high boost and may result in being boost limiting considering the high CR. Water/meth will help. Is the use nitrous completely off the table? I can envision properly controlled nitrous for this setup turning on at say 3K and off at 4800 and then we having the best of both quick spool and power. Time bomb??? Maybe so. I can only say that it has had many dyno pulls and runs great at that boost and CR. The engine management is Haltec E11V2. Would you vote for trying nitrous or K16?

[quattrorunner]

K16! The reason is the same reason some here choose intercooling instead of water/meth as their cooling agent for the charge. You never run out of it. I chose to use intercooling even though I bought a meth system and now see the reason, as I have come close to running out of water in the tank.
If you use nitrous, while it seems like the easy fix to your boost issue, you'll run out at some point, If you change to the smaller k16 turbos, or even go the single turbo and use a more user friendly metrhod to boosting, you'll love the much more streetable power available. And if you want to rev, go ahead and rev to 6600rpm, but start boosting sooner, that will give you more boost time and much more usable power.

[Miguel Antonett]

Originally Posted by JM2327

Here's the intercooler.

Peculiar set up!

How is its streetability and reliability?

[JFairman]

Is that a modified stock 930 intercooler? Looks like it..
I don't believe your 466 wheel horsepower because thats well over 500 HP st the crank and I don't think you can get enough CFM of air through that intercooler core to make that much HP from 3 liters, and the air coming out of that thing is going to be hot.

I'm sure it's fun to drive anyway.

[RarlyL8]

One of the reasons I would reduce boost above 6000rpm is to allow the K16 twins to remain efficient. Max HP is not of interest to me but may be to you so this is personal preference.
For the same reason I am not a fan of relying on injection of nitrous or MeOH to produce power. Great if you have engine control systems that can change all the tuning parameters when injecting combustion enhancers then switch them back when they run dry or are not used.
I quess the real question is what are your goals with this engine?

[quattrorunner]

Whats the exhaust look like?

[JM2327]

Originally Posted by JFairman

Is that a modified stock 930 intercooler? Looks like it..
I don't believe your 466 wheel horsepower because thats well over 500 HP st the crank and I don't think you can get enough CFM of air through that intercooler core to make that much HP from 3 liters, and the air coming out of that thing is going to be hot.

I'm sure it's fun to drive anyway.

Thanks for your comments. I can see where you might doubt these numbers but I assure you they are correct. You are absolutely right this is a modified 930 intercooler. Remember this is a rather small intercooler and not too many tubes for restriction. Intake air temperatures run about 140 F at full boost which is think is pretty darn good. Air pressure loss across the IC is about 2-3 PSI. Being from Texas A/C was of prime importance and the way the custom intake tube routes sacrifices had to be made in the engine bay. Think about a 3.0 liter Supra make over 1000 hp. It all in the flow of the turbo and this engine is capable of well over 500whp and the K24 18g turbos are capable of supporting about 700 hp. The boost control map is set at 19 psi and the electronic controller kicks in at about 5800k regulating the wastegates. So there is plenty of air left. I guess I’m more interested in mechanicals and not too concerned about the looks of the engine bay. Maybe that had some influence on your thinking. Sorry for being so wordy and hope this helps.

[quattrorunner]

I'm no expert, but even I can see where things can be inproved. Starting with the intercooler, that is too small and ineficient for high flow and boost. Those are good for low boost and even then proven not so good. In the stock location, it had air pulled through it by the fan and a good shroud, yours is farther back and probably doesn't get quite enough airflow through it. The turbos are good but not for your application, you would do much better with smaller turbos or only one of them, though it would not be quite enough for 400 hp. But two k16's might be great though probably still too big for my tastes. If I were you, I'd get either the k16's to reduce modifications, or make up a single turbo system with a nice common and proven turbo for your application that will make a great street car. Your setup would be fine for race situations maybe, but even still probably be better with a smaller turbo even then. And with a much better intercooler. I'd bet your getting detonation with prolonged high rpm and boost runs with that setup. Thats why the timebomb comment. With your high compression, you need a small turbo and lower boost. If you did that, you'd have a faster safer car. Maybe not quite as big a rush but the final result would be a faster better driving car.

[RarlyL8]

What transaxle are you running?

[MikeSchNail]

So far, I like everything you've done! I believe Brian is on to something...915 tranaxle? He can tell you more about those than me...

I say keep it like it is if you like it!, I love the low end "grunt" these other guys are talking about, but I don't think it's a good idea to move the boost curve lower in the RPM range in YOUR case...

You did say Texas right? Hot, but lots of open road where you can always have ALOT of air moving through the engine compartment, probably why your intercooler works fine

The lower back pressure of the larger turbos is probably a good thing, again, in YOUR case.

I'm currently obssesing over a low cost, franken-porsche monster built from hand-me-downs and pieces cast away or collected at low cost where the availability of parts sorta dictactes the build, prolly why I like your "hand me down turbos" so much

...so far I have a 993 Transaxle and an M64 RS flywheel, quite A LONG way to go...

[wjfk32]

Your statement says it all "60-130mph"

996tt- Guys are still using them and upgraded to a billet prop. Then they want more power they go with a meth system or e85. They are showing OVER 600WHP easily...I would leave it...U will eventually break something if the internals aren't beefed up.

Be careful if u have a 915.

Want boost sooner, upgrade the headers

I guess too much is never enough.


Walt