rad_951

Mark,

What is the weight of the E46 M3s you are competing against? Mine stock E46 M3 weighs approximately 3400lbs with a half tank of fuel, no driver. I don't know where all that weight comes from! Hardly any sound proofing in the car.

Last season a E46 M3 won GTS4 (not sure of the name of the class). It weighed in at 3000lbs with driver. I recall he has carbon fiber doors and hood. That makes me think the 928 has a weight advantage (lighter) over the E46 M3. Is this your opinion too?

Tony

FlyingDog

That's why I was asking for the dyno sheets.

While I was picking up 2 928s tonight, I was offered the opportunity to buy a supercheap S4 motor. I'll most likely stick with 16V, but I did have to think about it since my car is getting stripped to a shell and then built.

IcemanG17

This is the way to do it..............I have no doubts that if I had the time-space to take the widow down to a bare frame I could find all kinds of unneccesary junk to remove....I'd bet theres 50lbs of junk wiring-computers I don't use anymore....dump the pod and all factory gauges..probably 20lbs there, since the pod is fairly heavy..... Acid dip or blast the bare frame would be good for probably another 50lbs.....this is what Anderson did to get his SO light.... the sound deadening on the firewall is about 10lbs, etc.....

Yet one more thing to put on my "project" list when I finally get a real shop to work in (one day anyway)

I remember the rumors of Bob Devores super light race 928.....some said it was 2400lbs, but he seriously cut it up too....I wonder were it is today?

mark kibort

the e46 I compete against is a tin can too. Its completely gutted like any serious race car will be. He is about 3000lbs with driver. I come off the track about 2950 in most races. he has CF hood, and rear deck lid, with gutted doors. Its not as much power as the Grand Am Cup GS racer i race a couple of years ago, but that one was a full blown racer. (and had about 315rwhp). it has to put ballast in it to meet grand am specs, but for our SCCA races it runs with out it. about the same weight as me. the e36, like the dyno i have shown here, is 2750 with driver and has 290rwhp.

We are not talking about stock e46's like you see in T1, we are talking gutted race cars! all your weight comes in......... everything. seats, doors, windows, extra metal, bumpers, door bars, headlights, exhaust system suspension, etc.

to answer you question, NO, the M3 can be much lighter than the 928. the engine is much ligter, and the chassis can be made lighter as well. the Motorsport BMW chassis which PTG starts with (and many folks try and copy) weights 2550, WITH driver as it competed in WCGT in 2003. it latter was forced to put on weight to weigh 2700lbs. HP was in the 500 range.

mk

mark kibort

dont fight it. MAYBE if you are GREAT at cutting things out of the car, tearing it down to bare metal, re-wiring the car, sand blasting, you will end up with a chassis that needs to be re-tubed, like anderson found. in the end, he is 100lbs lighter. its not a big deal. 100lbs is a half a tank of gas. there have been fluke days where i have run my fastest laps on the 2nd lap. point is, there are so many things you need to work out before you go crazy with weight. its not like the BMWs or 911s where you can get those little tubs to 2200lbs or 2400lbs pretty easily. Think of the 928 like the vet or viper. its wider and can fit bigger tires than the BMWs and 911s and its engine has much more potential for power with less money and tune.

dont go nuts. again, you are going to be at around 2900lbs maybe 2850 if you go crazy, and the power is 220 for the 4.5, 230for the 4.7, 250 for the 4.7 pure euro, and near 300 for the 5 liter part euro 2 valver. You will be happier with the GTS4 car, but if the guys you want to compete against are in GTS3, then , go have a good time with them.

mk

FlyingDog

I'm not going to acid dip the chassis. I'll just remove every single part, sand off or media blast the paint off, and repaint. The car will have a much more substantial cage than Mark has.

mark kibort

Sounds like a big project. Good luck.

Look, from a lengthy experience of racing agaisnt the trick bmws and porsches like you are going to compete against , im trying to give you some objective information. POC, BMWCCA, NASA, SCCA, etc. Ive competeted more against these types of cars than anyone. I have a good feel of how we stack up with several different versions of our 928. after all , its powerplants have been stock, with all factory parts up until my last 3 races.

What ever you do, the building up the car from the ground, is not a bad thing and will get you at the weight you want. whether you run GTS3 or GTS4, you will have a better car. what ever you do, my advice to you is get the 10-11" rims in the rear with 305s and 275s up front. Id take 100lbs of penalty to run these tires vs a 285. Its something ive tried before and trust me, ill point in you in the direction of the things that make the biggest difference in lap time.
power, footprint, width, hight, suspension, aero, balance -weight, all are factors that are able to be tweeked from day one to have a very fast car.

By the way, what tracks will you be racing at? VIR? others?
How many races does GTS race per season?

I got you the dyno runs, I posted advice. I have videos of races on the bumper of any car you will ever run against. Let me know if you want to see drag clips, cornering , braking or all out lap comparisons against any of them with all sorts of variations of the 928.

mk

FlyingDog

My region is running 4 VIR full course events and 3 Summit Point Main events this year. If the car is ready when planned, I'll get 2 VIR and 2 SPR races. I may race Road Atlanta and NJMP with NASA-SE and NASA-NE.

mark kibort

So, you could expect 2:08-2:10s out of a 300rwhp 2900lb GTS4 car. How would that stack up with the GTS4 cars?

Im sure you will be fine whatever group you expect to run.

Keep us posted on the build up!

mk

FlyingDog

The official lap records are 2:09 for GTS3, 2:08 for GTS4, and 2:03 for GTS5. Our track records are race only, not even qualifying times count. Since the largest class in the Thunder run group runs 2:14-2:20, lap records tend to be a lot slower than the fastest the GTS3-5 cars can run. I know in practice some of the GTS3 cars are in the 2:06s and GTS5 cars are under 2:00.

mark kibort

and that correlates well with speed Touring times. Ive beaten several of their top guys in their cars at laguna . At worst case, my car is in the same ball park. (i.e. Prall, brandan davis,Nick Asayan etc) . They (top 10-15place cars) are running in the 2:08 range, so I suspect that what i am proposing for you could be in that range if you built the car like scot and i have built and set them up.
For a GTS3 to be about 1 second slower, that is believeable. a very light GTS3 car could be just a tick behind us, as we see with Bobcat (bob bradfield) in his built Rx7. (200rwhp and 2300lbs). see my video as to how he hangs with us, even at the turney tracks! eventually, he cooks his tires and fades back, but he is a force for sure. Hey, a 2050lb car is a force to be dealt with! This is my point. there is NO 928 in the world that can be made light enough and hang with this GTS3 type of car. sure its not GTS, but all you need is a radically built up M3 or 911 and it will be near the same performance, like we see in POC out west. So, thats why i push you to go GTS4. However, you make a good point about the want to race with the guys you know. So, go for it!

as far as practice times at VIR goes, sure, GTS5 is like what I have now and it better be speedGT like (their times are in the 1:57 to 2:00 for the slow guys)
The record speed touring car (GTS3-4ish) I think is in the 2:05 range for the top guys. Keep in mind that the fast GTS3 cars could also run slicks which was a debate as far as classifications. slicks can have more of an advantage than just a .5 weight to HP ratio. But, thats an entirely 'nother discussion.

mk

FlyingDog

The Touring car record is 2:05.650, but that was qualifying. I think the race winner's fast lap was 2:07 last year. Looking at the Speed schedule, there is no World Challenge event at VIR this year. The Bimmerworld guys must be pissed. VIR is their home track, only about 2 hours from Blacksburg/Radford where they live/work.

The GTS4 record for VIR is slow (although it's held by the same Rennlister who has the SPR GTS4 record). A lot of the GTS4 and GTS5 guys don't show up to VIR. Summit Point Main is a better comparison to my competition, but there aren't any pro events there. SPR records GTS3: 1:21.5, GTS4: 1:18.2, GTS5: 1:17.3, GTSU: 1:16.3.

IcemanG17

Mark A's cage and MK cage are going to be lighter than mine....... Mine is being built out of 1.75x.120 DOM which is 2.02lbs per foot vs 1.68 for the 1.75x.095 like MK or 1.78lb for the 1.50x.120 Mark A uses....

Heres a pic of whats done so far

mark kibort

scots cage is my old cage from my 84. its made from the same stuff. pretty heavy, and i think it worked out to be near 90lbs for his cage, but its minimal too. the Holbert cage, slightly more bars, is .095" rather than your .120, and it probably weighs about 10lbs less. anyway, scots car empty is still a very light 2680lbs with 2 gal of gas in the tank. (and he still can do the light weight starter, total sunroof removal, battery box removal, etc)

FlyingDog

I just picked up the car that will be my race car chassis. It's a non-sunroof early car. I already have the lightweight starter too. 16V is about 20lbs lighter than 32V. Scot's cage is really only 90lbs? I was told that a 944Cup cage is 145lbs including the plates in mild steel. Mine will be 1.75x.095 and I'm considering CM. Whatever the material, I'll probably have a professional TIG it.