I've nearly completed my single turbo 350 setup and am in the process of getting a new diff fabricated. In order to maintain SOME degree of streetablity (its a not city driver tho) i wanted to know what ratio you guys suggest/use inorder to get the best results before and during boost.

The setup uses a T4 V-ban with .75/1.32 (from memory :S )

Any help would be greatly appreciated.

NB: Mods: Sorry if this is kind of in teh wrong section but i really only wanted advice from teh turbo crowd. Cheers

 

Ratio? I dunno what you mean. A/R?

 

My bad guys. I was refuring to the diff ratio (gearing). 2.75, 3.08, 4.11 etc...

 

Turbo motors LOVE spooling so lower (numerically) gears are where its at. I have seen guys run better times with 3.08's than 4.10's just because they can stay in the boost long enough and they are now relying on horsepower to get down the track rather than gearing. I say go with some 3.08 or maybe next step up but thats it. It will also help you out in cruising considering you will be able to crusie at a much lower RPM than with 4.10's. Good luck!

 

It depends on the whole setup and not just the turbo, but in general with a turbo V8 (= lots of torque) you want taller gears, like he said.
It really depends on the powerband of the engine, tranny ratios, suspension (how well it hooks), etc.

 

Like everyone else said...it depends on your setup. I'm running 3.73s with my twin T3 turbo setup and I can tell you that in 1st gear I can only get 1-2 pounds until I shift to 2nd at which point it spikes up to 10 because my car revs up so fast in 1st. I'd say if you're running an auto stick with 3.23's or 3.08s, and with a manual, run 3.42s or 3.23s. I plan on swapping out my 3.73s for 3.55s and running a slightly taller tire.

 

Thanks guys. A little more info on the setup seems appropriate. Its a fairly standard L98 TPI, with a strengthened T-700 (standard gearing). The rear tyres are a very tall set of 15" Convos with 275/65 rubber.

The shop making up my diff for me says the supply all their diff standard with 2.75 gears.

 

Are you sure that they’re 275 65’s? those are some TALL tires.

Figure out what your trap speed goal is with what tires and roughly where your powerband is. Then figure on crossing the finish line at a 2-5mph higher a few hundred RPM past your hp peak and pick your gears to match that.

My formula is getting a Moser 9” with 3.50 gears and a locker

 

Yep



Front is stupidly high in this pic, since it was before all the turbo gear adn new springs.

Thanks for you advice, ill have to sit down and crunch some numbers.

 

Those sure look like 275 60s in that pic (about 28" tall), 275 65's would be over 29" tall and the front and rear edges of the tire would come very close to the fender lips

 

You may very well be right. Ill be heading over to the workshop thisarvo so ill be sure to double check. Shows you how long its been since i got to drive the poor thing.

 

Hi Luke,
Seems that you finally got your headers, where where they?
Any pics of the setup?

 

Yeah mate, they got here OK. Turns out they missed the firs tcontainer due to it being over-filled and had to wait for a 2nd

While i was waiting though i started wit all the body and chasis. Unfortunatly this turned into an entire tear down and rebuild.

So ever since this little project started I havnt even got the the engine stuff until now.

So far I have:

Bear metal respray
New Cowl Hood, and modded old hood to and open cut drag hood.
New wheels and tyres.
8 pt cage
700hp Fuel pump, Surge tank and FMU
SFCs

Last coat of paint hits it this weekend and then ill be able to start finishing the turbo gear. Stay tuned.

 

I feel sorry for you having to wait so long to receive the headers, good thing is that they finally appeared. Seems that you have been quite busy with your ride. I sadly have to say that the BBSDesigns GTA project car is running at almost dead turtle speed. I have all the parts for the new engine, all suspension bushings springs, shocks, etc.. almost no time even to write in this board(it's been a while since then) I just got a chance this past Sunday and fabricated from aluminum sheet an A/C delete panel with a 4" dia. duct for ram air induction for the driving compartment. I did it on a hurry and even burned my foot with a piece of molten aluminum that droped into my boot, OOUUCH! That is just the only progress the GTA has seen on all this past months. I also ditched the idea of running the Race TT kit, new plans, I will post by then.
Take care everyone!