Recomendations for lowering lap times - gearsets, suspentions, aero etc
 

Im contemplating either selling my car and buying a class race car or......the better of the two options, building my car up to compete in the local GT series.

I have:
6point cage
reliable 650whp engine package
modified factory gearbox - ok for drag...not sure for circuit.
Billet axles
factory brake calipers, larger cross drilled rotors - race fluid - good pads
coilovers and adjustable rear bars etc
RE Amemya wing
C West Front

I want the car to be up with the GT3 porsches.

I was thinking to get there I will need

Full brake upgrade - Calipers and rotors, ducting etc

New wheel and tyre package - I dont want to go flares so 17x10s or 11s maybe and slicks

Splitter and rear diffuser

What experience have you had with gearsets/sequential boxes??

What else should I be looking at developing?

The driver.

Go look at posts by "damian" - he probably has one of the more developed track FDs on the forum.

But there is still no replacement for developing the driver.

How far off of their laptimes are you? Are you competetive in the corners but getting walked on the straights? vice versa? Are they braking deeper than you? Are you getting fade? how is the car handling? What springs/shocks are you running?

Are you having issues with a particular gear at your tracks? Running out of rpm at the straight but not enough room for really using the next gear?

6 point cage, is it compliant with your local GT series rules? Have you looked at the rules? Have you reviewed your car to see how your proposed upgrades stack up against those rules?

The driver will be developed....this post is about the car and the car only.

Thats the sort of reply I was looking for!!!! THANKS!

How far off of their laptimes are you? - I will be able to answer that after this weekend. I have only had one sessions in the car so far with MAJOR brake fade. Didnt even get one full lap but was running 1:25s.....my goal is 1:12- 1:15s. As the car stands it should be somewhere around the 1:18-1:19 mark (replaced fluid and pads).

Are you competetive in the corners but getting walked on the straights? - The opposite. Im EATING everything on the straights, not cornering fast enough and had major issues with brake fade that should now be sorted.

how is the car handling? - Car is handling a lot better then expected. Im only on street tyres at the moment (yes will be purchasing slicks) and it wasnt all that tail happy, had a good feel around corners but just wasnt carrying enough speed. My biggest problem is not carrying enough speed around the corners to keep the car on boost (bloody HKS T51Rs are a little laggy).

What springs/shocks are you running? - Im having trouble tracking down the specs on the coil overs I have and spring rates etc, but Im working on it.

Are you having issues with a particular gear at your tracks? - No not really. I have a 4.8 rear end and it seems to work really well. Nearly topping 4th at the end of the two main straights and half way through 5th at the really fast part of the track.

Cage and all mods are well within the class rules.

What Im really after is an idea if it is going to be less money for the same lap times to develop my car, then purchasing something already built. - I REALLY want to keep this thing :)

Tursty,

Bill's comments are spot on however, bang for your dollar, driver development is key. Not clear on how much experience you have, but I'm betting you probably don't have a lot given the questions you ask, and in that case, comfort in your car, knowledge of the track, and comfort at speed will dramatically improve your laptimes without any real changes to the car. You mentioned not carrying enough speed, the more you drive the car the more comfortable around the absolute limit you will get.

Start with a decent set of slicks (assuming your rules allow it) or DOT R compounts). What pads did you switch to? What fluid? Are you adding cooling ducts to the brakes? Don't start messing with aero until you get mechanical grip figured out and you've really gotten a handle on how your car handles without it.

If you're not having issues with gearing, don't mess with it yet. Ratio changes are a double edged sword, it can help in some areas of a particular track, but hurt in other areas, and I think you've really gotta max out what the car can do before beginning to address gear ratios for a particular track. Really, are you prepared to be pulling and changing gear ratios every race weekend to suit a particular track?

Regarding your cage, is it really what you want for the rules you're allowed to run? I would imagine a GT series would allow a lot more mods than a club series like Improved touring would allow.

PaulC

Thanks for the reply.

The car will be driven by two people and they will be worked on...believe me. I have huge amounts of experienced drivers around me to work with so thats not a problem I have. To give you an idea though, I have about 4 years drag racing experience, a year circuit racing my old 4wd car and about 12 laps in this car.......IE im a beginner!

What I need to know is if its worth me selling the car and spending over 100k (NZD) on a porsch or lotus etc or if I could get similar performance after spending say 40k on what I already have.

Pads and fluid were decided after many conversations with a number of good race engineers over here. I went for Frodo race pads and Motual 600 fluid.....will be upgrading to Mobil 1 or similar if this still gives issues.

When talking gearbox changes, I was meaning gear changing more then ratios. Im going to ruin the syncros very quickly and wanted to get a feel for people opinions on whether to go dog or sequential with this sort of power.

Small break upgrades, slicks and driver training are all things Im already doing, but this isnt going to get me up there with porsche GT3 Cup cars.

The road I was thinking of going (if I keep this car) is New calipers and 2 piece disks, Frodo pads, Mobil fluid, ducting from the front bumper and maybe a bias if needed for the breaks.

New gearbox.....havnt decided on this yet and would like any advice I can get.

The reason I mentioned aero is because as it stand Im getting HEAPS on lift in the front. The bonnet is flexing up like no tomorrow and needs something done about it.
I was thinking, front splitter/under tray, ducting to the intercooler from the bumper and to the hood. A diffuser on the rear wouldn't hurt either.

I appreciate the feedback, good or bad. The main things I am looking for advise on is what can be improved on the FDs suspention and how, some good easy wins to stop the car from lifting in the front. And what type of gearbox to go for that will put up with my power levels and track abuse.

I just found a GOLD post about my suspension questions.

https://www.rx7club.com/suspension-wheels-tires-brakes-20/howard-colemans-fd-chassis-setup-723617/

I'll give another vote to improving the driver first. I would also suggest getting a data logger before spending all your money on upgrades. You can always transfer the driver and data logger to another car if you do decide to switch.

Slicks will help a lot but they will amplify every other problem.

Braking better with more grip, more brake fade.

Cornering faster, car will lean more, suspension changes needed to keep camber in check.

Higher spring rates? can the valves in your dampers control the spring now?

And finally as mentioned before, driver learning to drive the car all over again, any bad habits will transfer to the new set-up only when you spin in a corner you will slide farther(into a wall?)

Sorry about the, errr..., "blunt" comments. ;) Certainly no offense intended. From you initial posting I couldn't tell is this was a serious inquiry or more a boy-racer-wannabe.

There is a lot of good advice in the above threads. But in my personal opinion your takeaway should be "get the basics sorted out first (both car and driver)". Face the fact that with only a season of experience and a car that's "under development" you are going to be a backmarker no matter what. Look at it as a great educational opportunity! :)

Get your brake issues sorted out. Ducting is a requirement. Motul RBF 600 is good fluid. I'm not familiar with your pads. Are you seeing pad fade or fluid boiling? Did I mention that you need ducting?

Don't leap up to slicks too quickly. Good sticky DOTs (or whatever they call them down there) will be more forgiving and let you feel what the suspension is doing.

Howard's posts are very informative. Like I mentioned earlier, go read through Damian's posts - he documents his buildup pretty well. Pay attention to the order that he did things and why he did them.

For every dollar you spend on the car, spend one on the driver. You should have at least one good driving school planned for this season, if not two.


In any case, good luck with the build.

-b

If you're throwing this much money around you should consider Castrol SRF brake fluid over the Motul. Motul is really good and has the best bang for the buck(it's what I use in my car), but if you're still having trouble the SRF will give some extra breathing room.

You will find that your cooling systems will need major upgrades for road racing.

Water cooling

Oil cooling

Brake cooling

The proper sized components, and very good ducting are crucial to cooling, and cooling is crucial to running lap after lap and finishing a race with lap times as fast as you start a race (well, that and tire management too.)

^^ What he said, plus the fact that you obviously have too much horsepower in your motor and not enough in your brakes. You have to brake harder to decelerate to the speeds reached in the corners. My personal suggestion is to turn the power down a bit......Quite a bit in fact. You want to be about even with your competitors on the straights so that you can learn the desired lines and stop worrying about how much power you have to overtake. This mentality in itself makes you sloppy in corners because you are always thinking you'll make it up on the straights. To a point thats good, but its not the best reasoning to have. You need to learn the limits of the car and THEN push the envelope.

If you try to run before you learn to walk, you'll end up tripping the entire time.

Prior comments made about brake ducting are correct. 2 piece rotors are a good investment. Try different pads and see what actually works for you.
Do not use slicks until you are sure you have learned to be comfortable with the car and have been able to explore the limits before you make that step. If you jump into them too fast, you'll get sloppier. Faster, yes; but sloppier and not as fast as the well learned drivers.

it'll take some time to come into the feel of it.

i say driver also, 650hp/2700lbs is more power and less weight than the porsche...

datalogging is also good, dont trust the seat of your pants. the data should agree with what the seat of your pants is telling you.

otherwise stick to the basics first. alignment is important, toe and thrust angle particularly. tire pyrometer will tell you camber. in fact most of the really specific chassis tuning is based around the tire and driver. your job as a tuner is to make the tire happy, then the driver

for gearing you look at the engine dyno chart and corner speeds, you wanna try to match corners with gears, it'll be different for every track.

aero is a whole different deal, i dont have enough experience here, except to say that a front splitter does work very well, and doesnt require respringing the car!

Thanks for the comments guys. I really appreciate it.

The car is currently on a de tune - 480rwhp and thats as low as I can go unfortunitly (wastgate spring pressure and any more timeing out and lag becomes as issue).

You guys are all spot on regarding experience/seat time etc but Im dealing with that with the help of a number of mentors, so thought I would try and keep that out of this post.

Re the car. I have just purchased the new pads, fluids in. Next up is the ducting. Only question I have about this is, What is the ideal place to point the ducts to? Front of disc, front of wheel well etc?

Search around a little on 'brake ducts" and you'll find some examples. They should blow into the center of the rotor on the backside. If you still have the backing plates you can remove them and use them to fabricate a mount for the duct.

-b

You should have your radiator ducted directly out of the hood, it will also increase frontal downforce.

The fact that your brakes didn't even last one lap means that your rotors are not heavy enough.

By using friction, your Brakes convert your velocity energy into thermal energy. When you put the brakes on, the rotor temp rises very fast, maybe to 1200 deg F. Then you take your foot off the brakes, go around a corner, then go down the next straight. During that time period, your air ducts direct air into the center of the rotors, and cool the iron brakes back down to maybe 500 deg F. Then you hit the brakes for the next corner, and heat them back up again. If you don't have enough rotor mass, you will overheat your brakes on one stop from top speed down to zero miles an hour; no matter what your brake pads or calipers are.

I have to use 8.5 pound rotors (just the rotor, not the hub,) on my 2200 pound road racer in order to barely keep from overheating them. Since you have a more power and higher weight than my car, you will need much bigger brakes on your car. I would estimate that with 2 piece rotors on your car, your rotors would need to weigh around 12 pounds each in order to be able to absorb the heat you will be putting into them with 450 horsepower. If you go to higher engine power, your velocity will go up, and your heat loads into the brakes go up exponentially, not linearly with velocity. If you go to higher power levels, you will need much bigger rotors than the 12 pounds I listed.

Thanks for the replies again guys.

Ive put together a short term to do list now. (leaving out driver education...again haha)

Try harder to track down spring rates
work out rates vs swaybars and set starting point
Buy a pyrometer
Fabricate intercooler/radiator ducting
Fabricate break duct backing plates and intakes

Once I have got to the point where I am out driving these upgrades, I will be looking more seriously at removing ABS, custom break kit on the advise of my local race car prep shop and look at adding to the cage, removing more weight and going broke no doubt :D

Check out threads from damian and GooRoo on brake ducting and their setups. Might be here or in the Suspension subforum. With that much power, you probably need some real racing brakes. Some use AP, others StopTech, others Porsche take offs others RacingBrake. If you are clever at sourcing parts and fabbing brackets you might be able to get them on the cheap. There was a thread somewhere on this site about someone that used off the shelf champ car brakes with some fab work.

yeah Ive read through all of Damian and one of GooRoos posts....Pretty much have all the info I need now regarding brakes to make a start. Once I have a base it will no doubt just develop throught testing and trial etc.

Brakes are something I can sort out ralitivly easily....its suspention and chassis tuning that Im going to have to do a bit more research on.....again, I have what I need to make a start thanks to some excelent threads on here and will develop from there. Im rather confident that this car has the potential to run with the porsches etc with a decent driver.

Before you start looking at rims I'd really suggest looking at what's available for slicks and what you are willing to spend. You really need to start thinking about the race car at the tires first and then see if you can get rims that will fit your tires and then see if you can get a suspension to hold those tires to the road. If any point along the way doesn't seem to fit you need to start over at the tire. I'm not sure what the GT3 guys are running in NZ, but in the USA a new GT3 series is running the yokohama slicks. According to the series data they are running the soft compound up front and the medium in the rear. (to compensate for having all the weight in the rear). I'm notpositive which size they are running, but I'd be willing to bet as big as they can fit. Personally, I run a 230/625/17 up front and a 260/640/17 out back on my FC. The yokohamas are really the only option in 17" slicks. If you go up to 18" rims you can use the porsche sizes and there is a much bigger selection. For the power level you are running I'd go for at least a 280/650/18 out back in a soft or medium compound. I've only run the s004 (hard) so far, but this year I'll be upping the power and running the 280/650/18 in the rear in an s001 compound and the 260/640/17 up front (450 rwhp, 2300 lbs car). I'll keep you posted on my experience.

Basically, start plotting out ideas from the slick up, then the rims, then if you can get it to fit in the fenders, then what suspension others have used successfully. I'd also be very aggressive with the rollcage as that is really your only hope of tightening up the stock car body. Check the limit of the rules and tube as much as you can. I'd be looking to tie the front suspension to the cage and the same with the rear as much as possible. I'd also really suggest nascar style door bars because that extra foot of crush space makes you feel a lot better on the track.

Driving-wise, start out slow, take your time and build to speed. I've seen too many guys get out, push hard and eat a wall early on.

my $0.02
-Trent
www.rxracing.com

Much of what I would say is already stated.
But first, to re-inforce what has been started about the brakes:
You need a new, bigger setup - stock even with ducting is inadequate. No getting around it, the rotors are tiny for even a stock powered car. With over 400whp, they are absolutely marginal at best, and really more unsafe than anything else. As you get faster in the corners - your straightaway speed will pick up significantly - further stressing your already marginal setup.
Stoptech, a set of Porsche big reds, or any similar 13-14" front brakes and the 99+ RZ rear brake setup, (there are some fixed piston caliper rear brakes on the market but you lose your parking brake).
Slicks - stay away from them for some time. As an instructor - I can't tell you how bad it is for a beginner or intermediate student to be on sticky R compound tires,(tires such as the Kuhmo V710's, Hoosiers, Toyo RA-1's, etc..), or even worse, slicks. The limit of those tires are so high compared to good street tires, you can get away with absolute horrible driving and not realize it.
Tires with less grip are a great learning tool,(I'm talking about high quality summer street tires which are as sticky and good as the R compounds from 5 years ago). If your in a race series - street tires are not a good idea, but a good R compound,(mentioned above), is a better choice than slicks until you are a very advanced driver.
You should strongly consider a different car to do track days, in an environment that is less focused on passing guys,(non-competitive) and more focused on your driving - with the bonus of having someone in your car to talk about ways to improve. This allows you to develop your driving in a car w/less power -always a great way to learn - better in many respects, and by less power, it can still be a 300+ whp car.
But assuming you are sticking with what you have and going into a race series my suggestions:
-Upgrade your brakes
-Don't go with slicks - if you can, a very high quality street tire, if you don't consider that viable, a middle of the road "R" compound.
-UPGRADE THE DRIVER - I can't emphasis how much of a difference that will make - you will improve 10-15 sec per lap just on driving, 1-3 sec per lap on small car upgrades.
I do not suggest removing the ABS - you can be more consistent with it until you learn how to properly use the max of the brakes - and that will be a year or more.

Don't forget to pick up the complete Carroll Smith library:

http://www.pegasusautoracing.com/pro...oduct=TO%20WIN

Some of the info they contain is a little dated but I think anyone who is interested in motor sports should have these in their library.