i'm going to build a 400-500 bhp car in the very near future - it's a saab 9-3 and it's front wheel drive.
the car won't be used in drag races, it will be a daily driver and occasional track day car.
FWD cars are crap at taking this amount of power, there's torque steer and there's wheelspin.
What are the best upgrades used to improve handling in a high power FWD car?
So far here's what's on my list :
- proper suspension (bilstein / koni / etc)
- stiffer front end (a subframe brace and a strut tower brace)
- LSD
Is there anything else i can do - or is this basically about stiffening up the whole car and that's it? I mean the new(er) gen honda civics and mini coopers, they handle well and are FWD - are there complicated electronics involved (in the suspension parts) or is their suspension just basically stiff (and their chassis as well)?
In reply to andykauf :
What’s perceived as torque-steer is often 1 of 2 things: 1.) the front tires fighting each other for traction, or 2.) deflection in the suspension allowing unwanted movement of the LCA.
Being your DD you don’t want to go crazy & start replacing bushings with spherical bearings. Truthfully higher durometer rubber bushings would likely be the best option, but I’m not sure if any aftermarket bushings exist for you car? Poly bushings could work, but being your DD would require frequent greasing & even then possibly still squeak and/or wear prematurely.
A triangulated strut tower brace may help, but if your car is one of the latter GM cars it may already be pretty rigid? A brace that just connects the 2 towers & nothing else is mostly just decoration.
I don't know how Saab's control fore/aft engine movement, but in my GTI an upgraded torque arm and mount (what the torque arm bolts to in the subframe) had a massive impact on how well the car gets power to the ground. The next two things would have been struts and control arm bushings.
I don't have a limited slip, but that's a no-brainer for the horsepower you'll be running. At 220 hp my car can't even spin the wheels in first gear unless I dump the clutch.
In reply to Pete Gossett :
believe it or not, for torque steer there's already a solution for my saab, a steering rack brace that does wonders (at least for 250 bhp, where my car is right now).
there are poly bushes available - most decent handling saabs have them and it would the price to pay for having a dd and a track day car. they also make poly engine mounts, i hear they help with the torque steering as well, but the extra added vibration is not worth it...
premature wear is something i forgot about (thanks for bringing that up) - how many miles would it be ok to keep set of poly bushes?
the car (early GM, great engine still made by saab, horrible chassis) already has a (sort of) triangulated strut tower brace, it connects the 2 struts to the firewall, but it doesn't connect the 2 struts with each other - so i'll definitely need to build a proper one.
In reply to MrFancypants :
when you say upgraded torque arm mounts what are you referring to? a different mount (maybe full poly) or one with poly inserts?
struts and control arm bushings - noted.
my car is currently at 250 bhp (but has lots of torque) and i get wheel spin even in second gear (sometimes even third if it's a bit wet) - with 225 wide tires.
andykauf said:
i'm going to build a 400-500 bhp car in the very near future - it's a saab 9-3 and it's front wheel drive.
the car won't be used in drag races, it will be a daily driver and occasional track day car.
FWD cars are crap at taking this amount of power, there's torque steer and there's wheelspin.
What are the best upgrades used to improve handling in a high power FWD car?
So far here's what's on my list :
- proper suspension (bilstein / koni / etc)
- stiffer front end (a subframe brace and a strut tower brace)
- LSD
Is there anything else i can do - or is this basically about stiffening up the whole car and that's it? I mean the new(er) gen honda civics and mini coopers, they handle well and are FWD - are there complicated electronics involved (in the suspension parts) or is their suspension just basically stiff (and their chassis as well)?
Stiff suspension is the last thing you want in a high powered front driver. Stiff suspension means rapid loading changes, which means lots of times where the car is fighting you as the front traction situation changes.
IMO the suspension should be just stiff enough to keep you off the bumpstops in the worst situations, and no stiffer.
84FSP
SuperDork
12/21/19 10:39 a.m.
I would expect you to find the limits of the stock transmission. You will be tempted to put in expensive beefy axles. My personal thought is to leave them as the weak link and upgrade/protect the trans. You will get to be a pro at replacing cv joints.
andykauf said:
In reply to MrFancypants :
when you say upgraded torque arm mounts what are you referring to? a different mount (maybe full poly) or one with poly inserts?
struts and control arm bushings - noted.
my car is currently at 250 bhp (but has lots of torque) and i get wheel spin even in second gear (sometimes even third if it's a bit wet) - with 225 wide tires.
Sorry for the slow response, I have small children and an iRacing addiction, so I'm easily distracted.
I ran a search and it looks like the Saab community calls the equivalent part the "torque rod." The VW community calls them the pendulum and pendulum mount or "hockey puck mount."
In my GTI these parts come from the factory with large, not completely solid rubber bushings. First I replaced the "puck", which is the round black bushing in the picture below. The new one is metal and solid rubber. Next I replaced the "torque rod", which connects the engine/transmission to the subframe to control fore/aft motion of the drivetrain. I went with a piece that eliminates the bushings altogether and uses spherical bearings.
There's some added NVH with my new setup, but not so much that I mind. After the new rubber subframe mount was completely broken in the car is still perfectly pleasant to drive and it gets power down so well my GTI may as well be an AWD car when the pavement is dry.
Have you looked to see what the transmission can handel? If you are set on building the Saab I would built to 95% of that and call it good especially if it is our DD street car and you are working with a budget.
If 500 hp is what you want as your DD how reliable do you need this to be? I could build this cheep if you only need it to last one pull on a dyno but if you want 500 reliable hp that you are going to use with some frequency in a DD that you will be trucking kids around in that will get very expensive very quickly.
Have you considered a CTSv? I bet in the long run it would be way less expensive and getting 500 reliable HP is almost the out of the box spec on those.
I have a saab 93 sport combi with the turbo 2.0 in it and I considered messing with it but i then came to the realization that the car would be terrifying with 500 hp and to make it a reliable DD I would be north of 20k into it to make it a proper street car at those HP numbers. I then took a look at what 20k can purchase me and it was a no brainer. Made the Saab my daughters first car and use the 20k to purchase something that I can have fun with out of the box.
I ended up with way more than 500 hp in a AWD sedan that is just bonkers when in sport manual mode but is happy to do every day big car sedan stuff loping along. Even my wife likes riding in it and has no issues driving it. I have not dared to turn off the electronic nanny's yet. I need a runway or some other VERY large open place to do that.
Anyway just my thoughts on things. As a dad of 4 I had aspirations of what you are contemplating but after just not finding the time to even vacuum out my DD cars I came to the realization that for DD use an out of the box solution is way better.
Now all that being said if this is going to morph in to a weekend back road fun toy with some track time tossed in and you have some other DD transportation device I am all for you doing this. Hell I would help as making a 500 hp FWD Saab is something the world needs more of.
Will your car survive a track day at 250hp? Pushing that number to 400-500whp will bring all the weaknesses out. Take it out, break something, fix it. Unless you have a list of all the commonly broken things from other saab guys tracking 400+whp cars...
look up bluej on here....his neighbor (not on here) is a big Saab guy and has at least one that is pretty high horsepower....I rode in it and it was by far the fastest FWD car I've ever been in and didn't seem to have torque steer. Maybe he can put you in touch.
