What weight is your car at? I would cringe at the very though of putting on more weight on the front end. The GM time attack Cobalt was 2350 wet. My old Honda was 2450 wet. Loosing hundreds of pounds makes a phenomenal difference, but if you're still trying drive it on the street, it's practically impossible. AC, heater core, sound deadening, etc all need to go.

 

Exactly. The 1:1 scaling would remove the ECMs ability to decide that you only want half throttle even though the pedal is on the floor.

 

ummmm you guys know that you can tune out that situation don't you?

I stand by what I said before, 1:1 means whatever angle the pedal is at that the throttle would be exactly the same. Why would you want to go back to the '90's in technology when we can now make the throttle do (almost) anything we want it to do regardless of pedal position? Only reasons I can see would be that the particular OS doesn't support throttle mapping or the tuner just doesn't know how to do it. If we're talking about the LNF, we have pretty darn good throttle mapping, better than a lot of the LS ECU's had until the mapping tables were recently added to those.

 

il respond when i get home guys, extra busy, going to pick up the zr2 tonight...too bad it doesnt run. (number six rod bearing is gone and there is no oil pressure)

 

Hi Tom,

have you considered small shots of Nitrous during shifting on your races? It might be the simplest way to spool your turbo the quickest. But might not be the most cost effective in the long run.




I believe you already have a race radiator.

about heat issues during your race, how about adding the ff:
1.) instead of 50/50 water/meth,....just spray 100% water? Water will have more cooling effect.
2.) have a big as s oil cooler?
3.) have a bigger intercooler such as the Werk's Race intercooler? It is almost twice the size of Hahn intercooler.
4.) Besides having the biggest intercooler, also add air to water intercooler sequentially to have the most cooling effect? Then have an ice box to make sure its always supplying the coldest water.
5.) lots of fans
6.) scoop on your hood......lots of vent to release hot air?

 

I'm not following you. Why do we need technology to put the throttle plate somewhere other than where the pedal is? Having a 1:1 pedal leaves it up to the driver to perform- sort of like having a manual transmission.

Also, which tuning software are you referring to? We don't have access to anything like that in HP Tuners.

 

When considering twincharging a road course car, one thing to remember is that the factory water/air IC is not very good compared to what can be accomplished by an air/air. While I realize that you would have both, I feel that the heat exchanger for the water/air would have to be smaller than supercharged guys can run, and 28 minutes of boosting would have the water/air IC well over 200 degrees.

 

This is my feeling on the issue. I would much rather be able to modulate my throttle better rather than the terrible, almost non-existent pedal-TB response.

I believe he's talking about manipulating the DAL table. I definitely don't want 15+lbs of boost at 50% throttle... That's not opening it any sooner, that's just asking for trouble.

gmtech - I value your opinion and you offer great insight/advice but there is no reason to try and talk down to those of us who prefer something different. What we're after is the ability to have a more direct response with actual pedal to TB, somewhat similar to cable driven TB (obviously not 1:1 but more direct feel/response). Ever tried to roll into the throttle of your GXP to avoid traction issues and have the goddamn car go WOT anyway? I have and it sucks. I have tried a combination of things, including bringing TM by gear into the equation and while it helps, it's still not what others and myself are after.

Great idea! If you can't add more power, take away more weight!

More good ideas

 

whew lots of response on this.

Ok, to Matt, yep well aware the temps of the water to air can get wildly out of hand, I planned to remove the A/C condensor and run the heat exchanger in front of that then your zzp intercooler in front of that, Also I think I can nip the temp problem especially when I'm running a larger than stock pulley and the incoming air has already passed through an intercooler once.

Wang, my last weigh in was 2777 lbs wet loaded for bear with fire extinguisher (purple k type) full w/m tank (4 gallons) full fuel, and stripped of everything else including unnnecessary seats, trunk liner, subwoofer, rear speakers and the rest of the non essentials that can pop out friday night.

I do have an upgraded radiator, mine started leaking over the summer and rather than replace it with another GM part I manned up and had a Be Cool core built for the car, by the time I received it the 100+ degree track day temps were over. Next year will tell the tale but I can certainly tell the difference, the car is LOCKED into 187 degrees and it will stay there even if driven hard.

I'm working on the oil cooler issues, I certainly don't like the oil temps but I feel if I can bring down coolant to 210 or so I can get oil into the 290 range which is fine. The intercooler isn't the problem, I monitor IAT2 and it's just not high enough to justify replacing the factory intercooler right now, I am considering running straight water.

I've driven WITHOUT the hood just to see where that stands, and yanno it actually made it WORSE.

Wang I'm sure can relate to temperature problems, things get hot, even when your only out for a couple laps and you run a conservative tune. I tell people time and again if you think you can run more than 22psi, you will do one of two things, melt (read:destroy a ring land, which from pictures ive seen here has happened at least three times on high boost tunes, that's out of control pyro temps people, this is why you need to monitor that) your pistons/crack a sleeve or pass a piece of the turbo through the intake tract, the motor and eventually to the side of the turbo that will grenade it, ask me how I know.

I want to twin charge mostly because the motor is BUILT around the turbocharger it came with, with a cam profile to match, and because everyone can quote me a turbocharger in a variety of trims and inducer sizes but the fact is the water jacketed turbos start at more than twice the price and the few I found that might work just don't have a map that works with the motor efficiently in the range I intend the operate, the factory k04 not only does it's job well I believe the only way to complement it is to run a supercharger. I know I will have a challenge in mapping the waste gate duty, I know that it might be BEST to run BOTH bpv's I know that if I want to do this right the turbo still needs to do most of the work and the supercharger supplements it with possibly a slightly larger than factory pulley. I also know the DI is in the way, stop pointing that out in PMs I know this already. I also think that IF I did run a centrifugal supercharger I probably wont notice an efficiency benefit at such a low boost.

Anyways, yall brainstorm I need sleep.

 

Well damn, you pretty much shot everything down.

I just don't think you are going to get a roots supercharger to work with the stock k04. Only way I see that happening is to clip the turbine wheel. I doubt you do that.

I don't know why you don't think a Centrifugal would work. That would be the perfect type of blower to pick up the steam where your turbo falls off.

 

Exactly what I told him in a PM. Centri would make a very nice top end with the K04 set around 15psi for the low end. Would have an awesome power band.

 

so I guess, small squirt of NITROUS before the shifts for quicker spool will not be a consideration......

hmmmmm......TOM seems to be set with SC and K04. Hopefully, it works out. Time will tell.



Tom......ever considered running a compound turbo set-up like what I'm doing? You can have a k04 + GT30 or bigger turbo?

You'll have a stock looking set-up inside your engine bay................but rear mount the bigger turbo?

Or if you want a quicker spooling set-up, you can have a smaller turbo inside your engine bay........and the k04 rear mounted?


You don't need extra IC......since the long piping running across your car will act as the IC already.



It is alot easier compared to what I'm doing since I'm trying to put both turbos inside my engine bay which will require fabricating exhaust manifold.


You'll have a quick spool......and a bigger powerband.


Just some thoughts

 

That's not bad, but you could drop even more I bet. I don't even pop out my back seats. I like for people to come over and say WTF while looking at a fully interiored Cobalt. Plus I'm just out screwing around, nothing competitive.

You're right, the heat is brutal. Turbo charged cars are typically not road course friendly in terms of reliability. People have all these fantasies about turboed cars on track. Well, they're typically a PITA, and a total fail. That's why I'm thrilled that the TC holds up as well as it does. BTW - are you running a real oil temp gauge, or are you depending on the calculated oil temp via the ECU? It's just an estimate based on other factors, not a real temp probe.

The BNR turbo options are interesting. I'm slightly disappointed that it isn't BB like a real GT turbo, but it's twin scroll, and has a stock like CHRA, which means water + oil. Oddly, your temps may go down with a larger turbo, since it'll be running in a more efficient range, and 20 psi on a big turbo is more air than 20 psi on a smaller turbo, so you'll get more power too. You just have to compromise on range.

If you're hell bent on making more power, I'd say move up to an every so slightly larger turbo. BB turbos should also run cooler since it's less friction, and runs a lot less oil. Not many options for us here though. Werks has some from Precision (non water cooled), but they're all too big. Synapse has a GT2871 kit, but I dunno about their support these days. They seem to have left the Cobalt market. There are a few options that I wouldn't give up though. The turbo either has to be full dual BB, or twin scroll. Water cooling preferred, though the Precision options which have dual BB might be ok.

It's a shame that people on here give so many opinions with zero road racing experience, and zero data logging from a track session.

 

I hope you don't mean that the way I took it. Cause you just gave the exact same advice as most of the rest of us.

 

I've never seen a road course that will allow nitrous to be used on track....99% of facilities will not pass you for safety inspection with any sort of nitrous setup, so that would defeat the purpose of installing it if you couldn't use it.

 

Correct no nitrous no propane no bottled gas at all. I am looking into the rotrex centrifugal supercharger feeding the turbo. Since the computer won't freak out about that. I'm listening to yalls ideas and following up with research.

oh and my name isn't tom.

 

since you're thinking about Rotrex SC.................with my very limited knowledge about that SC, that kind of SC claims that it has a very instantaneous response similar to roots-type blower, and has a high effeciency range of a turbo...........................why not let go off the k04.....and just install this Rotrex SC by itself???????


that will give you the instant response you want, and high power output you needed.

 

army_greywolf......sorry my bad!

I thought you were Tom (greywolf) who also has LNF engine......that do HPDE road race and time attack at kappaperformance.com

 

I am having some misgivings about the posted efficiency of this supercharger (rotrex). It needs more research. If anyone KNOWS someone who has one and can get into contact with me I would love to know their dyno numbers and maf readings at peak.

 

Rotrex superchargers may have instant response(all superchargers do), but the boost curve is still terrible for a small motor. With much lower boost pressures through the midrange than they produce at max engine RPM, the power curve would be pretty disappointing.

It is also important to note that just because the compressor wheel in the Rotrex has adiabatic efficiency numbers close to turbochargers, this does not take parasitic loss into consideration. The power required to drive a supercharger is always greater than that of a turbo which utilizes energy that would otherwise be wasted.

Perhaps that biggest downfall of the Rotrex design- the friction drive system is very limited in max boost numbers. Having to keep the max boost relatively low for a 2 liter motor, I believe that this supercharger would offer almost no advantages over the stock turbo, while the disadvantages would be significant.

 

good point, I just feel having far more experience with roots blowers I can make that work and quite likely still make good on fuel consumption, temperatures and longevity.

 

nope but I know who he is. I'm probably the only turbo car that has gone this far without major problems, the honda and nissan in my class both went down mid season last year for blown head gaskets, I taught them how to machine the head for fire rings.

 

When you tear into someone as bad as you just did right there you better make DAMN sure your **** is right or these "*****" are gonna make it known you fucked up. As they should, IMO.

 

Ok so I decided to drop the twin charge idea, I am however going to look for a SLIGHTLY larger turbo, water cooled, ball bearing. If anyone has ideas, slip it by me.

 

i think these would work really well for u

Turbo Chargers: Borg Warner EFR Turbochargers