totse.com | Increasing Acceleration

ABnSW · #1 2008-10-04, 22:07

What would be the best way to increase the acceleration of my car? I've got a 1980 Pontiac Firebird Esprit with the Buick 231 3.8 v6. It's a strong motor and is a stump puller at low RPMs but takes forever to accelerate. I'd like it to be a little faster when I accelerate.

MunkeyQ · #2 2008-10-04, 22:33

First step is to make sure the car is in good working order...BEFORE you start to change stuff otherwise something will explode/fly apart/kill children. It will also probably cure the slow acceleration if there is a fault.

Check all your engine mounts, gearbox/transmission backlash, change the filters, check the HT leads for cracks, make sure your ignition system is working well (condensor, points, etc) get the carby reconditioned or clean the jets, clean engine grounding points, top up transmission fluid and clean its filters...and I could go on. Oh and change the fuel filter and make sure the pump is working as it should - no air being sucked in, etc.

Also adjust valve clearances and lap them if you fancy.

Before you make any real upgrades to the speed/acceleration, check your braking system to make sure it can put up with the increased load. A faster car will show up poor, malfunctioning brakes in the worst possible way.

Sponsored Link · #3 2008-10-04, 22:33

If its a torquey motherfucker, and you dont care about top end, taller gears.

Rocko · #4 2008-10-04, 23:08

Seconded, stick a 4.10 Posi in there.

ABnSW · #5 2008-10-04, 23:57

Quote:

Originally Posted by MunkeyQ View Post

First step is to make sure the car is in good working order...BEFORE you start to change stuff otherwise something will explode/fly apart/kill children. It will also probably cure the slow acceleration if there is a fault.

Check all your engine mounts, gearbox/transmission backlash, change the filters, check the HT leads for cracks, make sure your ignition system is working well (condensor, points, etc) get the carby reconditioned or clean the jets, clean engine grounding points, top up transmission fluid and clean its filters...and I could go on. Oh and change the fuel filter and make sure the pump is working as it should - no air being sucked in, etc.

Also adjust valve clearances and lap them if you fancy.

Before you make any real upgrades to the speed/acceleration, check your braking system to make sure it can put up with the increased load. A faster car will show up poor, malfunctioning brakes in the worst possible way.

Engine mounts and Transmission mounts have all been replaced within the last 4-ish months. Carb was just replaced about 2ish months ago as well as plugs and wires. Brand new fuel pump a week ago, changed filters then. I know I need to repair my brakes first. I've got a leak in the rear brakelines, I just found where the leak is when I was changing my muffler. I'll have to check the Ignition system and the engines grounding points.

So the best bet for now, will be to change the gears? I don't even know the gears I've got now. It's hard as hell to find out information about my car online since its the 6 cylinder. I was talking to my dad and he suggested that I should put in a 3.93 because it'd give me a little bit better acceleration, but not hogging on the gas, but if I was looking to jump off the line to put in a 4.10.

Nereth · #6 2008-10-05, 02:56

The final drive raio IMO is only a fine tuning mechanism to help you get the most out of your engine - it desn't really swap acceleration for top speed etc unless you have a 1 speed transmission. I don't think you will get what you are after from a gear change unless you changed the engine for another and the old system is poorly matched.

Let me illustrate with an example.

When accelerating with your racier gears (eg 4.10 instead of 3.x), as you first start out, acceleration will be higher for a few kph, but you will have to shift at a lower speed, and then acceleration will be lower for a few kph, and eventually the revs will get up and you will be accelerating harder, again, than you used to at that speed, but then you will need to shift earlier, etc. The process continues and the losses fight the gains.

How optimal your gears are at a given speed is proportional to how close your RPM is to the power peak at that speed. Lower gears will have you getting closer, faster, as you first start accelerating, but they will have you shifting earlier and leaving the power peak sooner as well. There is also shift time and the fact that it will slightly 'focus' the RPM range you are operating in over the top end, i.e. the needle won't drop as far when you shift, but I don't think that change will be large enough.

The solution to 'I don't have enough acceleration' is usually:

a) More power.
b) Less weight.

and occasionally

c) less drag.

Pick one of the first two and go for it, I recommend 'a' because it's normally a bit easier and you won't sacrifice your comfort, and it's not like you care about fuel economy in an 80s firebird right?

ArgonPlasma2000 · #7 2008-10-05, 03:15

The 3.8 is a really nice motor, but its not a powerhouse until you throw a turbo or a supercharger on it. For instance, the Series II 3800 has 240 hp, but that block has a FWD bolt pattern, so you will need a tranny bolt pattern adaptor. Isn't the bolt pattern the same as the Chevy trannies? Several Fiero shops sell transmission adaptors for fitting Chevy engines to the FWD transmissions: http://www.v8archie.com/v8Archie/Prod2.htm

I'm pretty sure they will work in reverse.

Ouster · #8 2008-10-05, 10:00

Smaller wheels, a well performing exhaust system from the manifold back, and a "better" cylinder head will all help with acceleration. Once you've done a few things, try and get to a rolling road to optimise your engine set up.

ABnSW · #9 2008-10-05, 20:08

Quote:

Originally Posted by ArgonPlasma2000 View Post

The 3.8 is a really nice motor, but its not a powerhouse until you throw a turbo or a supercharger on it. For instance, the Series II 3800 has 240 hp, but that block has a FWD bolt pattern, so you will need a tranny bolt pattern adaptor. Isn't the bolt pattern the same as the Chevy trannies? Several Fiero shops sell transmission adaptors for fitting Chevy engines to the FWD transmissions: http://www.v8archie.com/v8Archie/Prod2.htm

I'm pretty sure they will work in reverse.

I'd love to put a supercharger on my car, but I don't think there are any pre-made supercharger kits for the 1980 3.8L. I'd probably have to have it custom made. I don't know so much about a turbo. I don't like turbo lag. I'd like something that's kind of cheap, but just for a little bit of power. I'm not looking to spend a whole lot. A rear end swap wouldn't be too expensive. I've found a 4.10 posi for about $400. It'd be nice if that's all I'd need to get a little bit faster off the line. Also, the Transmission is the TH350, which is a chevy tranny.

ArgonPlasma2000 · #10 2008-10-05, 21:15

If you get a properly sized turbo it's going to work better than if you get too large a turbo. If you recall the 1980 turbo Trans AM it had retarded turbo lag because it had a funny carb setup and the turbo was way too big. The Buick Rivieras and Grand Nationals didn't have that big a deal with lag.

If it's only $400, it's cheap and it works for what you want it to do. Probably will get better results with that than anything else that cheap.