Pt-88

[shorti28]

Anyone using this turbo other then me? I'm having a hell of a time spooling it, any suggestions? Car has run 10.20@131 @1.46 60ft launching @15lbs and running 24lbs @ atco for the downs ford/buick day(last time out)

[GN280CI]

Originally Posted by shorti28

Anyone using this turbo other then me? I'm having a hell of a time spooling it, any suggestions? Car has run 10.20@131 @1.46 60ft launching @15lbs and running 24lbs @ atco for the downs ford/buick day(last time out)

set-up is ........

[shorti28]

Here's my setup!

4.1 STAGE 2 MOTOR
BUICK MOTORSPORT CRANKSHAFT
ROSS 8 1/2 TO 1 PISTONS
BUICK MOTORSPORT RODS
STAGE 1 CHAMPION ALUMIINUM HEADS (CHAMPION CNC RACE PORTED)
TITANIUM KEEPERS
1.65 ROLLER ROCKERS
SOLID ROLLER CAM
72 MM THROTLE BODY
82 LB. INJECTORS
PRECISION 88 TURBO
3 1/2 INCH DOWN PIPE
HEADERS MUFFLERS TAILPIPES ALL STAINLESS STEEL
TORQUE CONVERTER IS A.T.I. 5500
TRANS IS TH. 400 WITH TRANS. BRAKE AND AN AIR SHIFTER
REAR IS FORD 9 IN. WITH 35 SPLINE AXLES
3.50 GEARS AND SPOOL
WITH DISC BRAKES FRONT & REAR
SX FUEL PUMP
SPEED PRO ENGINE MANAGEMENT SYSTEM
FIRE SYSTEM UNDER HOOD AND DASHBOARD
FIBERGLASS HOOD & BUMPERS
6 POINT ROLLBAR
METCO REAR SUSPENSION
CAR HAS FULL INTERIOR & FULLY OPTIONED
TO DATE, CAR HAS RUN 9.97 AT 138 MPH (PREVIOUS OWNER)

[GN280CI]

the curve fuel its ok ? the last owner run whit the same set-up ?nothing to change part

[shorti28]

I put on the ported gn1's with the titanium retainers. The last owner ran 9.97 @ 28 lbs. The fuel tables are good but perhaps a little lean @ idle. I was told fattening it up @ idle may help, any ideas? Right now if I don't stage first I'm left sitting for a sec or 2 building.

[HighPSI]

A 5500 convertor should definitly get things done. I had a LOT less than that when I had a similar combination. What's your timing and A/F at spoolup?

BTW: When you do get it sorted out, watch your injector duty cycle closely. That fuel pump/injector combo probably won't get it done.

[DonWG]

Originally Posted by HighPSI

A 5500 convertor should definitly get things done. I had a LOT less than that when I had a similar combination. What's your timing and A/F at spoolup?

BTW: When you do get it sorted out, watch your injector duty cycle closely. That fuel pump/injector combo probably won't get it done.

I agree with Cal. The tuning at pre-stall is very, very important to getting the quickest spoolup. Since you are running a transbrake, it should be very easy to tune the engine while on the transbrake to get the quickest spoolup. I do mine right on the rack in the shop. Set your transbrake, bring the engine up to the typical rpm you use to creep into the stage light, then WOT it on the transbrake and take a note, or datalog, of how quickly the engine reaches stall AND, more importantly, how high the stall speed is. Play with mixture and timing until you get the quickest rpm rise AND the highest stall speed out of the converter. As you narrow in the tune, you will notice, just by feel, the engine becoming snappier and the stall speed of the converter rising to a higher level. The more torque you put to any particular torque converter, the higher the stall speed will be. You can use the stall speed of the T/C to roughly gauge whether you're increasing torque or not. Kinda like using the T/C as a water brake dyno. Works pretty neat. Make sure you give the converter time to cool between tests. This procedure builds up a fantastic amount of heat in the T/C.

Another reason to have a transmission with a transbrake.

What cam specs are you using? That stall seems awfully high. But maybe an 88 needs that much stall. If all else fails, break out the juice!

One more note about target A/Fs. When I tune, I try to ignore the A/F number. Of course, you want to stay safe as you're dialing the tune in, but you should be searching for the best power and response. When you think you have found it, keep going richer until you feel the power drop. Go back to the previous best setting and then is the time to take note of the A/F ratio. That will be the A/F that your engine likes. Depending on countless variables every engine is going to have its best A/F number. You must find what your engine likes. At the highest planned boost levels on the fuel map, I will richen it, up to four tenths (gasoline readout) to stay on the safe side.

[HighPSI]

Originally Posted by DonWG

Set your transbrake, bring the engine up to the typical rpm you use to creep into the stage light, then WOT it on the transbrake and take a note, or datalog, of how quickly the engine reaches stall AND, more importantly, how high the stall speed is. Play with mixture and timing until you get the quickest rpm rise AND the highest stall speed out of the converter. As you narrow in the tune, you will notice, just by feel, the engine becoming snappier and the stall speed of the converter rising to a higher level. The more torque you put to any particular torque converter, the higher the stall speed will be. You can use the stall speed of the T/C to roughly gauge whether you're increasing torque or not. Kinda like using the T/C as a water brake dyno.

I wouldn't try and reach stall speed. Once you get over the "hump" that turbo is gonna try and run away from you. On that convertor, stall is probably 6-7000 rpm depending on how much boost you hit it with. I would set a two-step for your launch rpm and log how long it takes to get to it. Just my .02

[DonWG]

Originally Posted by HighPSI

I wouldn't try and reach stall speed. Once you get over the "hump" that turbo is gonna try and run away from you. On that convertor, stall is probably 6-7000 rpm depending on how much boost you hit it with. I would set a two-step for your launch rpm and log how long it takes to get to it. Just my .02

That is a very good point. I was thinking of my PITA tight torque converter. Then again, you could do a quick run up and shut off to ????? rpm (determined by the size of connected balls), take a datalog, and do a study and adjustment after.

I'm going to correct my previous post I made. At pre-stall rpms you should be tuning for lean best torque or just a tad bit richer than lean best torque. After the engine gets over the hump, as it was put, maintain that A/F ratio until just at the higher boost regions ramping the mixture to rich best torque by maximim planned boost. This strategy seems to work best for my situation. Your situation may differ. Give it a try. You might like it.

[DonWG]

The procedure I outlined in the previous posts is a really good way of discovering the best A/F ratio for your engine without having to pay for dyno or track time. And you don't even have to do a full run. The point where the engine is on the hump of the T/C is going to be your number. You can use it for the rest of the fuel map, except for max boost levels where you might want to richen it for a safety cushion.