Sexy

 

Stock JWT kit, which is 6.8; however, the thin atmosphere in Colorado Springs (~6000 feet altitude) makes it absolute pressure of about 3.2, which equates to about 6.0 or so.

Still very nice though!

Dave

 

Congrats on the awesome Kit Dave. So it finally got done on Sat night. I wish I could have stayed and seen the car finished.

Would definitely love a ride in that thing!

I've always wondered how the boost thing worked in CO. So even though the stock boost is 6.8, the actual boost is only 6.0 because of the thinner air. Not sure how the controllers work, but I thought they would just keep it at the 6.8.

So if I am correct you would have to set the boost to about 10 psi to equal a car at sea level boosting 6.8 psi. (10.0 psi equals effective boost of about 8.4 which covers the 6.8 stock boost, plus an additional 1.6 Psi to cover the Denver atmospheric pressure loss).

That might be way too complicated to try to convey over the forum.

 

No, you've got the right idea. It's why turbo's can "compensate" for the elevation while N/A and SC engine's don't. The key is in how it's set up. Due to the MAF sensor, his engine is going to take about the same hit from the altitude as everyone else.
A racing engine like used for the Pikes Peak Hill Climb, might use a MAP sensor instead to run boost based on the manifold pressure. If the wastegates are run off this pressure, then the turbos will be allowed to provide more boost as atmo pressure drops to maintain the same manifold pressure. Of course, as the boost changes, so does the compressor efficiency, so it will never be a perfect substitute for lower elevation. But pretty close.
Will

 

No, the UTEC uses a MAP sensor, which is what I am using.

What ends up happening is that absolute pressure is equal to about 3.2 psi or so, which is about 6 psi over the ambient pressure here in the Springs. The wastegates should be good to 6.8, so the calculations might be a bit off, bit it's still good.

Dave

 

Wow... Get too tech for me. IMO: You have a aweet car w/ a sweet set-up.

 

i would love to ride in that thing, i want to see how that TT setup is going to feel on my car!

 

Well, just filled up the gas tank, the first full one after the TT install, and figured my mileage. Still getting about 22.5 mpg! Not bad, not bad at all!

Dave

 

Do you have to install new BOV's to get up to 8 or 9 PSI? I thought you could do that with that stock kit. I wouldn't want to go any higher than that on a stock motor.

 

Since its using internal wastegates, I imagine the actuators are run off the compressor outlet for safety reasons. Thinking about it, either a MAP or MAF would have some compensation for altitude. If the wastegate was set for 6.8 lbs of boost it would be based on an absolute pressure of 21.5 psi in the compressor outlet. Of course, that actuator would have less pressure acting on the other side to keep it closed against the boost, so the thinner air would allow it to open earlier. So.. I guess that's another reason to run the actuator off of manifold pressure, besides better boost threshhold.
Will

 

The BOV don't have anything to do with boost control. When the throttle closes, they vent the return surge of air in order to prevent it from reaching the compressor vanes and causing damage. In a MAF system, it should be recirculated, but people like the "psssh" sound.
I think you meant the wastegates. They control the flow of exhaust energy around the turbine, and therefore dictates the amount of boost the compressor makes.
Will

 

Thanks Will for the info and the correction. I knew there had to be something I was missing.

The TT shootout article had the JWT TT kit at 7.8 PSI doing 432 RWHP SAE. Most kits at stock boost seem to be around 380 with exhaust, so I was hoping the kit would compensate for the lower pressure at Denver and you could get non corrected RWHP close to those numbers.

So if I am understanding correctly:
To get an actual 380 at the wheels here in Denver you would have to set the boost to 9.3. (12.2 PSI actual pressure in Denver + 9.3 PSI to equal the 21.5 absolute pressure the stock kits get at sea level.)

I guess this makes sense, Juztin has his TT kit set to 9 psi and he is showing 452 at the wheels corrected which is about 380 non corrected. It just seems dangerous running 9 psi of boost and seeing 452 rwhp on a stock motor. But I guess the engine would only "feel" 6.8 PSI boost and 380 rwhp.

My goal is to get about 390 rwhp non corrected up here in Denver on a stock engine, so I am just trying to get it all figured out.

 

Exactly. The absolute pressure stays close to the same that way. With most kits, I guess you have to manually run the boost higher to compensate. And I guess remember to turn it down if you're going to go to lower elevation. Since the wastegates on these turbos, both the Mitsu and the Garrett, are run on a diaphram type actuator, they will produce less boost at altitude than at sea level unless manually set higher. I know on racing systems they can set the external wastegate to run off the engine's MAP sensor, so that it is activated on a signal from the ECU when the maximum absolute pressure is reached. Since there is no diaphram with atmo pressure acting against it, it is an absolute boost system. So as the cars gain elevation, the boost levels will progressively get higher to maintain the absolute pressure. Champ Car uses a similiar system to precisely control the boost delivered for their push to pass. I checked one out while at the Motorsport Engineering department at CSU, but I can't remember the details well enough to relate them as facts. In any case, the turbo's can "compensate" for the altitude to an appreciable extent, and some advanced systems will do so automatically.
Will

 

with the stock 7.5psi spring my MAP was showing 6.6psi. I figured the pressure loss was from the IC. Either way, my manual boost controller is having a hell of a time keeping a consistent boost (since we barely bumped it around 2 psi to 8.5-9psi) so it gets all over the place and fluctuates pretty bad. Going to be fixing that here pretty soon by just going to 11.5psi wastegate springs. Boost @ the MAP should be in the 10.5-10.8psi range *hopefully* with a very smooth and climbing powerband to redline and not a jaggedy and fluctuating power delivery from the varying boost pressure. Hopefully hit the 500's and see if the engine/JWT clutch can hold it.

b.t.w., my uncorrected hp on the 452 run was 368. for 390 uncorrected hp you will most likely need to be in the very high 400's.

 

I'm all confused now....

Dave

 

Actually, on a serious note, it looks like my injectors (stock, with stock fuel pump) are running near max (88% duty cycle or thereabouts) and before I raise the boost, I will be getting bigger injectors, a Walbro 255/lph fuel pump, and maybe a AAM return fuel rail.

Dave

 

what size injectors does JWT include? FYI, 440's run out at 9.5psi on a stock exhaust (would probably run out at less boost with a 2.5/3" TD open exhaust)

 

They are stock (which I believe are 370's) So to raise the boost all that much you need to go to bigger injectors.

On the other hand, if you go to much higher than that, you start getting rougher idle. Not too bad with 550's or so, but any of the huge injectors can get a rather rough idle.

I will probably go with 550's, but I am not exatly sure yet.

Dave

 

Dang, I can't believe how much Denver affects us, even with Turbo kits. Checking around, 452 is pretty typical rwhp for a Greddy TT kit at 8.5 psi at sea level, so it seems to be cranking out the correct numbers. My question is, does the engine feel the stress of 452 or 368. I would think 368, which means your kit should be very safe as is. Getting the exhaust I think would bump your uncorrected power to very close to the 390 range.

If you get the exhaust kit and your SAE number goes to the high 400's and you never blow your engine, then we will know it's the uncorrected number that matters!

 

550's here with the UTEC (N/A at the moment) and almost purfectly smooth idle. It is rough at times but not bad.