best a/f for spooling large turbo

[tom j]

What seems to work for you guys gt4276 turbo's and larger. What a/f do you guys target say up to 10-12 psi when you are running 25-30psi. Timing also?
This is with leaving on a trans brake so I'm trying to accomplish a faster boost ramp from 12psi to full boost. This is also done with a t-pro

 

[SloGN]

to help with turbo spool up you can add fuel and then lower the timing to get the headers hot to help with the spool-up. what kind of engine managment are you using?

 

[tom j]

I was under the impression that hot air moves faster so wouldn't a leaner af work better that adding fuel. I just got done reviewing a data log using tuner pro and I am at a af ratio about 11.0 at as low as 4psi. I really don't start building boost until 3000rpm and it really doesn't take off until about 4200rpm. This is on a trans brake launch. I also don't achieve max boost of 28psi until 5600rpm and I shift at 6000rpm. What would it do if I were to target a leaner 12.0a/f so maybe up to 4400rpm. This is with using a t-pro with a gt4276 turbo and e85. I feel there is alot to be acheived in this area. My best 60ft of a 15psi launch is 1.47

 

[Jay Wicks]

to help with turbo spool up you can add fuel and then lower the timing to get the headers hot to help with the spool-up. what kind of engine managment are you using?

Not unless he's running a clutch car.

 

[bison]

Id add timing and fuel. Mine is around 12.5:1 and tapers down to 10:8:1 at 28psi. I run as much timing as possible for the octane im running. Im at 36 degrees at under 12 psi and it tapers down to 22 degrees at 28 psi. Not a 42-76 but they will be similar. More compression always helps too.

 

[gbsean]

What seems to work for you guys gt4276 turbo's and larger. What a/f do you guys target say up to 10-12 psi when you are running 25-30psi. Timing also?
This is with leaving on a trans brake so I'm trying to accomplish a faster boost ramp from 12psi to full boost. This is also done with a t-pro

assume you have the t-pro chip set for faster spool up...

Launch Assist: When enabled, Launch Assist will improve turbo spoolup while brake-torquing for improved launch when racing. This mode is not intended for street use and does put a lot of heat into the turbo exhaust, headers, and exhaust valves. It does do a good job helping launch a turbo that is too large for the torque converter stall speed. When activated, Launch Assist reduces engine torque and increases exhaust temperature. Launch assist will activate when the throttle is between 50 and 85% and vehicle speed is below 5 mph. When Launch Assist is working, the Check Engine light will flash.

Spool fuel: The WOT AirFuel ratio during spoolup can be varied using Parameter 14. For the first 1.5 seconds at full throttle, but below 10 psi boost pressure, the AirFuel ratio is modified by Parameter 14. Default value is 8. Each increment higher will richen the AirFuel mixture by 2%, each increment lower will enlean the mixture by 2%.

Maybe you can talk to Bob and see if he can change the spool Fuel in the chip.and the amount of time at full throttle...just a thought....

 

[tom j]

assume you have the t-pro chip set for faster spool up...

Launch Assist: When enabled, Launch Assist will improve turbo spoolup while brake-torquing for improved launch when racing. This mode is not intended for street use and does put a lot of heat into the turbo exhaust, headers, and exhaust valves. It does do a good job helping launch a turbo that is too large for the torque converter stall speed. When activated, Launch Assist reduces engine torque and increases exhaust temperature. Launch assist will activate when the throttle is between 50 and 85% and vehicle speed is below 5 mph. When Launch Assist is working, the Check Engine light will flash.

Spool fuel: The WOT AirFuel ratio during spoolup can be varied using Parameter 14. For the first 1.5 seconds at full throttle, but below 10 psi boost pressure, the AirFuel ratio is modified by Parameter 14. Default value is 8. Each increment higher will richen the AirFuel mixture by 2%, each increment lower will enlean the mixture by 2%.

Maybe you can talk to Bob and see if he can change the spool Fuel in the chip.and the amount of time at full throttle...just a thought....

I believe the launch assist won't work because I run a 400th and have no speed sensor. Can't I achieve the same thing of "spool fuel" by reducing the target af down low and add timing in that area.

I checked to see were my timing is at it's as follows
3000rpm-30deg
3500rpm-27deg
4000rpm-24deg
4500rpm-23deg
5000rpm-23deg
5500rpm-22deg
Maybe I'll bring the timing up to 35 until 4000rpm since that is were my boost starts to really start coming in. If spool fuel worked up untill say 15psi that might be the ticket. Should I play with timing first or fuel.

 

[SloGN]

From what i remember when i used to run bailey's extreme chip when the launch assit and the spool fuel were activated together on the direct scan you could see it load the motor up rich and then pulling the timng back to make the headers get hott.


Burning the fuel in the exhaust will make the turbo spool pretty quick as there is less space in the exhaust than in the cylinders. i do this with my fast system and it works pretty good.

 

[TurboBob]

retarding the timing and adding some fuel will heat up the turbo and can improve spool and launch. but it reduces the torque at the wheels and puts a strain on exhaust valves, head gaskets, etc....

Because it reduces torque, it can make launching easier on the brakes. but the function must disable when you launch.

If you run a trans-brake, you can tune for max power to push the torque converter higher and launch that way.

Try both and see which works best for you.

Bob

 

[GNVYUS 1]

TurboBob you gotta help get that plug and play coil on plug setup so then we can do a 2 step and really get things moving during the launch.

Bison's way of lean with timing would be a good place to start. If you can actually control the fuel ratio and timing per 100rpm then start it off even leaner and then ramp it up as soon as you launch.

 

[bison]

TurboBob you gotta help get that plug and play coil on plug setup so then we can do a 2 step and really get things moving during the launch.

Bison's way of lean with timing would be a good place to start. If you can actually control the fuel ratio and timing per 100rpm then start it off even leaner and then ramp it up as soon as you launch.

The converter will stall the highest the way i explained it. It actually goes richer as boost/rpm increases. Its at about 13:1 until 10 psi or so then goes leaner.

 

[tom j]

UPDATE- So I leaned out below 4000rpm 12.5 to 12.0 and added 2deg of timing. Now I can't seem to hook the car leaving at 10psi when I was hooking it before leaving at 15psi. It really comes on fast when compared to before actually to fast.:biggrin:

 

[bison]

UPDATE- So I leaned out below 4000rpm 12.5 to 12.0

 

[SloGN]

UPDATE- So I leaned out below 4000rpm 12.5 to 12.0 and added 2deg of timing. Now I can't seem to hook the car leaving at 10psi when I was hooking it before leaving at 15psi. It really comes on fast when compared to before actually to fast.:biggrin:

actually you richend it up. 12.o is richer than 12.5 the bigger the number the leaner it is. so 15.0 is leaner than 14.0. hope this helps before you kill the motor

 

[TurboBob]

I think what he means is:

was 11.0 - 11.5

now 12.0 - 12.5

so now its leaner than before.

 

[tom j]

actually you richend it up. 12.o is richer than 12.5 the bigger the number the leaner it is. so 15.0 is leaner than 14.0. hope this helps before you kill the motor

See post #3

I know that 12.5 is leaner than 12.0

 

[bison]

The converter will stall the highest the way i explained it. It actually goes richer as boost/rpm increases. Its at about 13:1 until 10 psi or so then goes leaner.

I f'd up on this post. The last word should be richer. Sorry about the confusion.

 

[GNVYUS 1]

Good to see it worked out, what timing are you launching at now?

12:1 still seems pretty fat for 10psi but if you can't keep the tires under that then time to move on to suspension.

I was messing around yesterday with my buddies AFC in his Turbo Talon and you can clearly hear how fuel makes an impact on brake boosting. Lean does help wake it up, I started at 14:1 at 0 boost starting from 1500-2500 and it makes a difference in how fast it will get up.

 

[Blazer406]

....... Lean does help wake it up, ........and it makes a difference in how fast it will get up.

You still talking about turbos? :biggrin:

J/K....

Back to topic....... :wink:

 

[tom j]

Good to see it worked out, what timing are you launching at now?

12:1 still seems pretty fat for 10psi but if you can't keep the tires under that then time to move on to suspension.

I was messing around yesterday with my buddies AFC in his Turbo Talon and you can clearly hear how fuel makes an impact on brake boosting. Lean does help wake it up, I started at 14:1 at 0 boost starting from 1500-2500 and it makes a difference in how fast it will get up.

Timing is at 32 at 3000rpm which is were it begins to spool and it tapers down to 30 at 3500 about 10psi. Wot timing is 21 at 30psi.