TT Turbo Questions

[Projecting IMAX 70mm]

I am first going to give you a background on why I think this might work. I drive a turbocharged car a Mitsubishi Eclipse (FWD) GST (and I am the farthest thing from a ricer you can get, everything under the hood and completely stock exterior) Anyway...I keep reading about how traction is the limiting factor on TT Vipers. I am going to rattle off an idea and anybody please correct me if I am wrong as it is harder than heck to get any tuner to tell you their setup (of which I do respect)

So our problem is traction...Looking at all the videos I have seen it is getting of the line with minimal wheel spin. What I have done to cure this problem is a (Apexi AVCR) multiple stage electronic boost controller (all I have seen on Vipers is a low boost/high boost toggle switch) How it works is.....lets say I have one huge turbo that kicks boost right off idle. I can actually program this AVCR to blow off any boost until I either specify a RPM or a gear or both. It is also programmable to kick in boost in 500rpm increments. So instead of burning out forever at the staging lights when I should be halfway down the track this AVCR gives me the advantage of getting a rolling start before any boost kicks in. Thusfor I already have forward momentum built up and it gives me a better "hookup" and not so much wear and tear on the drivetrain.

I have tried to find something for Vipers along the lines of a AVCR bur the closest thing I can find would be a VEC 2 with a custom card for this but then again I do not know the limiting factors of the VEC 2 to this application if there is even any. I have looked at the AEM Engine management and I have not found anything saying it would have the function to do what I am describing the AVCR can do.

I am not trying to be a ricer and try to ask stupid questions, But I do consider myself a racer who looks at the technical aspect of everything. I have powered a FWD Turbo car to 11.8 sec 1/4 mile and this setup mentioned above solved a lot of my problems. I know I can get better times out of it but I have since sold my car to start my business and bought another Eclipse so it will be awhile before I can get all "tuned up" again. On the TT Vipers, Are they the same size turbo or are they different sizes?

Cheers,
Ben

Apexi AVCR Info

 

[Torquemonster]

You are correct.

AEM allows you to do that. It also has traction control capability (which has not been used yet on a TT to my knowledge).

Most tuners keep their turbo sizing to themselves - but they tend to be similar to each other as the space is tight where they are most commonly mounted.

 

[Projecting IMAX 70mm]

I had no idea the AEM could do that. Does anybody know if Heffner used the boost function for the 9.569 @ 155.51 run he did not to long ago? I am not exactly looking for turbo sizing (where it would be cool to know though) as much as I am looking to see if they use two turbos of the same size. Or do they have a lower spooling turbo to carry boost through let's say a 1,000rpm-3,000rpm rev range and then have a more aggressive turbo kick in at 3,050 and carry it until redline. But I kinda lean toward using two of the same size turbos because method last mentioned is usually used when you have a small engine (like a 4 ******) But were talking about a 488ci or a 505ci engine..the only way your going to get turbo to lag is if you strap a turbo the size of a 747 engine on the exhaust manifold. How does the AEM have traction control? It must use the ABS computer and apply caliper pressure to manage traction????

Cheers,
Ben

 

[CHAD]

That's a rediculous idea!

 

[RedGTS]

The AEM traction control is based on wheel speed. It must be programmed based on a set rate of acceleration, and then if it senses more than that (which would be wheelspin) it will reduce fuel or timing, or both, depending on how you program it. So like most other aspects of the AEM there is some programming talent involved, but once it's done it's supposed to work very well.

 

[Projecting IMAX 70mm]

So basicly what AEM calls traction control would be to cut power until it senses grip and then will let you tap the engine for it's power once you know it's hooked up to the road? If so I can see where that would work. Very clever.....

Cheers,
Ben

 

[RedGTS]

Exactly. The driver would just keep the pedal to the floor and the EMS would reduce power somewhat until the wheel speed fell back in line with potential acceleration, then it would restore full power.

 

[FE 065]

If the AEM could simply compare front to rear wheel speeds, it could sense wheelspin very quickly... (unless you were pulling a wheelie)

 

[1MEANSNAKE]

Keep in mind guys that the Apexi AVCR is much much cheaper than the AEM Units. This is a much cheaper option to control boost/rpm increments on a budget.

The Apexi AVCR is a nice unit and is widely use in the import racing industry!

 

[RedGTS]

Keep in mind guys that the Apexi AVCR is much much cheaper than the AEM Units. This is a much cheaper option to control boost/rpm increments on a budget.

But who puts turbos on a Viper on a budget? I mean you don't have to spend $40k anymore, but if you're going to spend $20-30k, and you're going to have to have some kind of engine management anyway, the difference between an AEM and the other options (e.g., VEC2) is $2k or less. I don't see a market for these in the Viper world, right now.

 

[RedGTS]

Also, I checked the AEM user manual, and to correct my statement above, the AEM traction control uses ENGINE acceleration as an input, not wheel speed. Apparently this is because not all cars have wheel speed sensors, and on the ones that do many use an external signal processor to read the input. Therefore to remain plug-n-play, they went with engine rpm because every car will have an input for that in its EMS. Otherwise the principle is the same--you configure the maximum possible engine acceleration without wheelspin, and the accompanying sensitivity tables, etc. to come up with a table that works for your particular combination.

 

[Torquemonster]

and to answer another question - all current TT Vipers I know of use one each bank - same size each side.

Nobody has done a twin in series yet - but that is just a bad idea on a 500 cube engine anyway unless it is for all out racing and you are using one to preboost the other. For street it would be dumb - too complicated for no gain over a conventional twin.

Ask Jason Heffner how much lag his TT Vipers have out on the highway.



NONE. So why even consider two in series?

 

[CHAD]

Ask Jason Heffner how much lag his TT Vipers have out on the highway.



NONE. So why even consider two in series?

Why would I want to let a Busa get ahead, even if it is only for an instant. Lag sux.

Although now that you mention it, purposely letting one get out front and then blow past sounds like fun. I'll have to try that.

 

[Torquemonster]

you don't need to worry about no Busa Chad! You've got those things covered with two parallel turbos

I don't think you'll run out of boost on that setup anytime soon

 

[CHAD]

I concur.