Turbo guys, gearing?

[s8v4o]

I know ideally 3.55's or 3.73's are considered good turbo gear because they "load" the car well but I'm curious as to who's running 4.10's? I know the S197 is fairly heavy so I thought 4.10's might not be that bad. When I load the numbers for a 28" tall tire, 4.10 gears, and of course 4th gear I come up with close to 122MPH.

So how many turbo guys are running 4.10 gears? Do you like them or do you want to change your gear. For those running different gears have you thought about stepping up? My calculations for 3.73 puts trapping in 4th gear at close to 134MPH at 6000RPM. I guess that's fine if you're putting out over 650HP.

The reason I'm asking is because I want to go as fast as possible (within reason) N/A. Then see what numbers I can get with the nitrous kit I just installed. While working my way up to a turbo kit. I'm trying to choose my future mods wisely so they can be good for me now and later when I have a turbo kit. That's the reason behind me asking about the 4.10 gear and turbos.

 

[TurboPete]

Runs better with 3.27s . Stays in gear loaded longer pulls harder .


Pete

 

[JeremyH]

3.55 are perfect, I think the 3.27 ia a good idea too. Buddy went to 3.73s in his turbo stang and and it made 1st blow the tires off at anything more than half throttle and the other gears too quick. He switched back to 3.55s afterwards.

 

[s8v4o]

Runs better with 3.27s . Stays in gear loaded longer pulls harder .


Pete

Using my same logic/math while using your RWHP 3.27's are very ideal for your setup. I wouldn't be surprised if your car traps close to 145-149 MPH. If you were only running 500 RWHP do you still think that 3.27's are still ideal? Do we throw ideal gearing out the window for the sake of "loading" the motor?

3.55 are perfect, I think the 3.27 ia a good idea too. Buddy went to 3.73s in his turbo stang and and it made 1st blow the tires off at anything more than half throttle and the other gears too quick. He switched back to 3.55s afterwards.

Sounds like your buddy needs better traction! lol. I noticed your 60' is 2.1. Do you think that is because of your gear choice? If I opted for 3.55's that would put me at 140MPH (750+HP) at the top of 4th gear and only like 107MPH at the top of third. Neither of those options seems very drag friendly. Even 3.73's would put me at 135MPH (650HP) at the top of 4th gear.

Has anybody datalogged boost with gear changes to see exactly how the boost curve actually changed? That's something I would like to see.

 

[PNR Welding]

3.73 gears here and I shift at 6500 and go through the traps at 140mph. Never made a complete pass on the dyno, so dont know the whp, but 140mph has got to be around 700whp. This was with a 1.56 60' due to the tire spin and letting out to gain traction.

 

[circusboy]

3.31's here. I had 4.10's when I first put the turbo in, but my clutch was slipping the entire way down the track lol. I had to go to 5th gear at about 1200' or so. 3.31's are much better. At 477RWHP inthe heat I hit 141 MPH at the top of 4th on the dyno

 

[TurboPete]

Using my same logic/math while using your RWHP 3.27's are very ideal for your setup. I wouldn't be surprised if your car traps close to 145-149 MPH. If you were only running 500 RWHP do you still think that 3.27's are still ideal? Do we throw ideal gearing out the window for the sake of "loading" the motor?

I still feel the 3.27 will load more which will help the car pull harder regardless of hp.
On the dyno at 6k trap speed is 152 mph. but thats not taking into consideration for Converter slip at the track , so 145 is a good guess I think.
I cross the 1/4 around 5500 , well that was with the previous tune and set up , I changed Turbo , made 150 more hp in the mid range , and lightened up the car, so Im not sure whats going to happen now. I changed to the 3.27 because since I had stock heads and not making much power after 5600 anyway I wanted to keep the car in the power band longer therefore a gear change would put me where I needed to be.

Pete

 

[US-1]

I had 3.31 gears with a 26" tire and they were great. Unfortunately....I was pushed to a 28" tire and lost quite a bit of elapsed time until I upped the starting line rpm. Anything from a 3.27 to a 3.55 works pretty damn good. Only time I'd run a 3.73 gear is with a 28" tire.

And to answer your question a few posts back.....yes, with a turbo engine you toss the "ideal gear" crap right out the window.

 

[Vashthe3rd]

yes, with a turbo engine you toss the "ideal gear" crap right out the window.

Yep
3.27's, stock 3.31's, or 3.55
I'm on 3.31 and it works great, I've considered 3.55 but that's as far as I'd go. That extra load helps. The power you put out earlier in your RPMs from the bigger load vastly out weighs going above 3.55s until you're running a big tire. Even then, 4.10s are going to be ridiculous

 

[5.0Shocker]

good info, keeping my 3.31's for the turbo build

 

[pqtiii]

I had 3.31 gears with a 26" tire and they were great. Unfortunately....I was pushed to a 28" tire and lost quite a bit of elapsed time until I upped the starting line rpm. Anything from a 3.27 to a 3.55 works pretty damn good. Only time I'd run a 3.73 gear is with a 28" tire.

And to answer your question a few posts back.....yes, with a turbo engine you toss the "ideal gear" crap right out the window.

When running 28in tires, is it better to run 3.73 vs 3.31? I need to rebuild my rear and have extra 3.73 and 4.10 gears. Running 28 MT slicks with 3.31 and 5000rpm @finish line. Don't want to waste the boost in 1st though.

 

[TurboPete]

Here's another example , Ive always run a 28" tire .
When changing from 3.55 to 3.27 I went from a 1.46 60ft to a 1.40 consistently.

3.27 or 3.31 are the best gears in my opinion on a Turbo Car.
3.55 to 3.73 are best for PD blower cars .
3.73 to 4.10 or 4.30s are best for Nitrous or S/C cars.
And run a 28" tire on those combo's for best traction.

If you have a motor that is built for 7000 rpms then a 26" tire will accelerate quick but the the traction off the line could be a challenge.


Pete

 

[US-1]

When running 28in tires, is it better to run 3.73 vs 3.31? I need to rebuild my rear and have extra 3.73 and 4.10 gears. Running 28 MT slicks with 3.31 and 5000rpm @finish line. Don't want to waste the boost in 1st though.

3.73 on yours.

 

[s8v4o]

Thanks for the responses guys. I'm going to push the car as far as i can on the stock longblock N/A, then nitrous so for now I will install some 4.10's. I can do the labor myself on the gear changes so when the time comes to install the turbo kit I can reinstall the 3.31's that are in the car right now or use the 3.55's that's currently in my mustang SVO. Never hurts to have a bunch of different gear options sitting on the shelf anyway. Thanks again guys.

 

[s8v4o]

Here's another example , Ive always run a 28" tire .
When changing from 3.55 to 3.27 I went from a 1.46 60ft to a 1.40 consistently.

Thanks for the concrete numbers to back your hypothesis. Due to the dynamics going on here with turbo cars liking lower numerical gears I guess you could say turbo cars are more "green" lol. No parasitic drag on the engine either. Turbos FTW! Hey Pete I know your car is built and runs E85 so have your calculated you highway mileage. I'm curious to see what you get.