ECU remap, nitrous, & supercharger

[longassname]

Now that the car sat over night and had time to cool I've pulled a spark plug and inspected it and sent pics to the tech at ngk I talk with. The insulator is perfectly chalky white so we aren't anywhere close to being in danger of fouling the plugs. The center electrode isn't greatly discolored so it isn't running too hot as is and the ground strap has a lil carbon on it that's chalky white showing that it's burning off propperly again showing the temp is right for the setup we ran yesterday. Since we seem to be running a good deal richer than what will give the most power especially at higher rpms we are going to rejet to lean things out. By leaning out things will get hotter and since there isn't any danger of fouling the plugs we are going to go with a plug another step colder. I just pin the order for the bkr8eix plug which should come in friday. I'm also going to get a bottle heater. Our nitrous bottle pressure was a little low yesterday (850 psi) which would have added to our problem of being too rich. This will leave us running again on saturday or sunday so look for the new #'s then.

I'm going to try some new gear selection methods and see what we can do about handling the horsepower better at launch. I was looking through the service manual at the transmission section and the difference between 1st and second gear is considerable but I'm going to try launching in second with the manual button on nonetheless and manualy shift into 3rd when it feels right. If I'm reading the diagram of the shift patterns in power mode correctly it doesn't shift into 4th at wide open throttle until you are well above 112mph/180kmh. This means if I can launch in second gear with no traction loss but still push that big a gear ok we'll only have 1 shift to go through from second to third. Hopefully the manual shift is quicker and then we can finish in 3rd gear. If this works ET time should be greatly improved.

If I have to launch in first the first gear change isn't until 55mph. In this case I will try launching without the nitrous armed, with the manual button on and first gear selected. I will then arm the nitrous and it will engage after we're rolling, then manualy shift to second and third when it feels right. If this proves to be the best route we should be able to launch with the nitrous armed off the line after installing larger tires.

[NeedForSpeed]

Michael,

My '92 speedo read 125 mph when it shifted into 4th at full throttle. It will be a fine day when we need fourth in the quarter.

How do I know?

I was on a long straight country road when I pulled up behind a Harley at a stop sign. Pulling away from the sign, I went around him at full throttle. He went around me like I was parked. I lifted at 125 with the Harley well in front.

Where's my supercharger?

[svxhunter]

Originally posted by Phast SVX


AWD car's have lower MPH's then most cars :better low speed acceleration lower top end acceleration due to drivetrain loss. A 101mph AWD trap is. on par for his run time.
phil

SVreX at the Grassroots Motorsports Challenge- AWD, stock tranny (slipping between 2nd and 3rd), no internal engine modifications, no ecu remapping, lightened, underdrive pulley, crudely modified air intake, bolt-on dry nitrous 75 hp shot, stiffer suspension - 13.8 1/4 mile at 100.8 mph.

[longassname]

Originally posted by svxhunter


SVreX at the Grassroots Motorsports Challenge- AWD, stock tranny (slipping between 2nd and 3rd), no internal engine modifications, no ecu remapping, lightened, underdrive pulley, crudely modified air intake, bolt-on dry nitrous 75 hp shot, stiffer suspension - 13.8 1/4 mile at 100.8 mph.

That car must be awfully stripped down. The svx is 3700 lbs plus driver..the usual allotment is 200 lbs...that's 3900 lbs...the dyno runs i've seen plotted for stock svx's have been around 176 hp at the wheels...lets say you got the full 75 hp and lets forget about estimating the loss to the wheels and give you a full 250 hp at the wheels...stock weight would have you running a 14.55 @ 93.6mph.....if you were stripped down to 3150 you'd calculate out to run 13.8 @98.5 mph.....so if we assume your time is accurate then both your car is extremely light and awd would seem to have a higher trap time at the same et than what rear wheel drive calculators predict.

[svxhunter]

I have no idea how to convert the rear wheel calculators for AWD, but its clear to me they would be extremely inaccurate. I think the car has an 80/20 torque split on hard acceleration. That would indicate it acts more like a FWD car than a RWD.

Yes, the car is significantly lighter- by about 700 lbs. It's not a street driver.

I forgot 1 other modification- we were running 215/45/16's. They look a little dumb, but offer improved acceleration due to the smaller diameter.

NO wheelspin. 2.044 60' times.

[svxhunter]

That was not an attempt to brag, only to agree that the 1/4 mile time should be improved at 101 trap speed.

[Chiketkd]

I will start a new thread. A buddy of mine pointed me towards a DSM website that has come up with their own formula to calculate AWD horsepower from 1/4 times and trap speeds - the formula can be switched around to calculate ET and Trap Speed.

-Chike

Originally posted by longassname
Using the standard rear wheel drive drag calculators it does look like the trap speed I go should yield a better et. Some of the difference should be attribited to loss of traction but that doesn't explain all of it. Some more of it is likely the fault of the gtech. I'd still be curious to know more about the differences to expect in the calculations due to being awd. Does anyone actually know? I mean geniune information not just hypothesees and guesses. If so maybe we should start a thread discussing it.

[longassname]

Originally posted by Chiketkd
I will start a new thread. A buddy of mine pointed me towards a DSM website that has come up with their own formula to calculate AWD horsepower from 1/4 times and trap speeds - the formula can be switched around to calculate ET and Trap Speed.

-Chike

good deal, post the link here

[longassname]

Actually, i just found the thread and it's the same online calculator that is commonly used for rwd cars.

[Chiketkd]

I was told the formula was slightly different, but if it is the same then I was misinformed.

If RWD cars have a drivetrain loss of 15-20% (depending on transmission) and AWD cars have a loss of 20-25%, can that formula be modified in any way to accomodate this?

-Chike

[longassname]

Originally posted by Chiketkd
I was told the formula was slightly different, but if it is the same then I was misinformed.

If RWD cars have a drivetrain loss of 15-20% (depending on transmission) and AWD cars have a loss of 20-25%, can that formula be modified in any way to accomodate this?

-Chike

The formula is for horsepower at the wheels so drivetrain loss is not a factor

[mbtoloczko]

Originally posted by longassname


That car must be awfully stripped down. The svx is 3700 lbs plus driver..the usual allotment is 200 lbs...that's 3900 lbs

If you have time, is there a scale where you can weigh your car? When my '95 L AWD still had an AT in it, I took it to the local dump yard scales, and it weighed in at 3490 lbs with 1/2 tank of gas. I had installed lighter wheels/tires and Stebro exhaust system which is lighter than stock, but the ATF cooler and my custom strut springs add back a few pounds.

[Chicane]

I'm like 90% sure the SVX doesn't weigh that much. From all the sites I've seen, it says the SVX weighs about 3525lbs.

- Rob

I'm going to cornerbalance my car next week on our scales, I'll give you guys an exact figure on my '94 LSi's weight.

[huck369]

Originally posted by Chicane
I'm like 90% sure the SVX doesn't weigh that much. From all the sites I've seen, it says the SVX weighs about 3525lbs.

- Rob

Rob,

The advertised weight that Subaru posts, is dry weight...no gas, no oil, no water, no washer fluid, no brake fluid...I guess you get my point, motorcycles do the same thing, but by the time you add all the fluids, a bike weighs 10-15 pounds more than the advertised weight, and a car holds a lot more fluids.
This would explain the differance in weight of a driven car and the manuf. advertised weight.
Just my thoughts on it.