Just got my LSJ 2.0 (05 Cobalt SS) powered sand rail back from the dyno tuner. My results are depressed because I run a VW Bus transaxle with 15% power loss. For comparison does any body know how much HP the stock GM tranny robs?

I also tested it with 33"tall 12.5" wide tires and the Dyno guy said that had a dramatic effect on the numbers. I'm having a hard time trying to figure out how much it effected it. Anybody know or want to guess how much a 33" tire affected the numbers?

213 HP @ 6000 RPM, 210 ft lbs at 4200 RPM. At 2180 torque heads straight up. It runs like a bat out of he11 in a 1500 lbs car but the numbers are low due to tranny and tires. Anybody want to guess how low?

Mods:

LS1 Chevy throttle body
2.9 pulley
ZR1 Corvette inter cooler
42lbs injectors
Headers into high flow header muffler
MEFI4b computer

Oh...And it does second gear wheelies when the boost kicks in. twothumbs
Any thoughts? Thanks
Stump

 

dafuq did i just read?

 

thats pretty dam good the numbers arent low is the engine still running stock injectors

 

what the hell i dont understand anything? MEFI4b computer??? and it almost sounds like you have tunning problems

 

i'm thinking troll

 

lol that was my exact reaction too

 

there is a lsj powered sand rail down here on a complete stock engine it ******* rips hard

 

If I remember correctly, these cars usually lose 7-8% through the entire drivetrain (that includes wheels, hubs, cv shafts, etc.), so losing 15% just from the transmission is huge. Let's not forget that those 33" x 12.5" wheels and tires are going to weigh a ton. As if the huge increase in weight wasn't enough, since the tires and wheels are rotating items their intertia also eats up power, and their large diameter only amplifies this loss.

 

42 lb. injectors.
The computer is a popular MEFI controller used on all sorts of race rigs. I don't know much about it other than that so I mentioned it.

 

I don't think those are bad numbers on a 2.9 pulley with that transmission and wheel/tire setup.

A normal LSJ with a 2.9 will likely be in the 225-250whp range depending on supporting mods and tune.

 

the guy running the one here is on the stock pcm your also on the outside edge of those injectors whats the afr set at on wide open throttle

 

I don't know the AF numbers but the tuner had a blank check to get it perfect. ADS dyno tuners in Arizona are the top of the food chain around here. They did a lot of work like throttle body mods and a better knock sensor to keep it safe at WOT. It's fueled rich and timing is pulled back until it hits operating temp then its like the power is turned on. Throttle response is spot on to steer with the rear and that was priority over WOT runs. I have confidence they did all that could be done. I was also running 30% LL100 AV gas for the tune and plan on 50/50 from here on out. Hmmmm Is AV gas richer or leaner than pump? Maybe I should stick with 30%.

 

there is no way you are running rich with 42's on a 2.9

 

Not sure if real person.

 

the buggy should be tuned for wot also and a bigger set of inj should be put in also

plenty of people do it

 

i ran a 94% duty cycle on a 3.1 on 42's. i can't imagine an LSJ would be much that different as far as duty cycle goes

 

It's only rich on the tune when the engine is cold. The tuner said a lot of SC engines blow up when they get pushed hard before they are at full operating temp. I guess it has a different fuel map when the temp sensor reads low. That was my understanding any way.

 

Is duty cycle the amount of time the injector is on or how much it's open? I'm guessing that 100% would be the injector wide open for as long as it can be open.

 

Don't get too hung up on the dyno numbers, they may not exactly be accurate, especially if you aren't sure exactly what gear you should be using on that exact dyno. For example, Cobalts are supposed to be dynod in 3rd gear. I punched it in 1st on the dyno just messing around, and hit over 600 tq!

What I'm saying is that as the car is well tuned, and you are happy with how it drives, then don't worry about it.

 

hit them up
CBM Motorsports - Custom Built Motors - Offroad, Marine, and Hot Rod Engines

 

CBM is where the computer, throttle body and wire harness came from. They sent a tune and software with it. I called them first and talked to the owner. He asked me to bring him the car for a tune or pay thru the nose at ADS. I payed thru the nose but it was local and now that its done it was evident that CBM was not all that well dialed in with this configuration. I mean how many folks rip a Cobalt engine out and twist it into a buggy? Not their fault. For reference the throttle body plate blocks air to the idle air sensor so it needs to be drilled and a Cobalt knock sensor is not the best one for their computer. Besides that it needs to be tuned a whole lot from their box tune. Such a cool engine it's surprising that swaps aren't more common.

 

people are failing to look at the rotating mass of the 33x12.50's tires.

 

Look at post #8