Scottie-GNZ

Anyone out there running a 27" tire on the rear of their Z? I would like to see a side view picture. I assume if anyone is, it is probably for drag racing only. Let me know what diameter front tire you are also running.

That was my car before GN power. I am going out on a limb to say I was probably the 1st L28ET to use SDS.

Not sure I understand what you are saying. This pic was taken in 4/99.

You will stand out only if you act like one :D OK, I understand the need for the wheels now.

I can give you the part # off my .82 and I can also get a stock GN housing and take the measurements but I really think you need to drop the idea of using the GN turbine housing. Now, there is a 4-bolt to 3-bolt adaptor that would allow you to use the GN housing but I am not sure if the 4-bolt pattern will mate up to the L28ET exhaust manifold. The main problem you will have with your current setup is with the wastegate hole diameter being too small. When you start approaching higher boost levels, the small diameter hole just cannot bleed off boost quick enough and you will have boost spikes. It is not uncommon to have stock housings modified to fit over bigger wheels and have the wastegate hole made bigger. After all, I am doing just fine with a stock GN .63 modified to fit over a P-trim wheel. You just have to run a couple more psi of boost and sacrifice some MPH, but the smaller housing will spool quicker and get you quicker 60' times. Bottom line is the smaller housing will probably result in quicker 1/4-mile ETs. Of course, it makes it easier if you are not trying to do this on straight pump gas. I see you having 3 options: 1. Install a bigger wheel, get the stock housing ported to fit over that wheel, enlarge the wastegate hole and replacing the puck with a larger one that will fit over the larger hole and seal properly. 2. Try to make the GN housing work. Assuming it will bolt up to the center section, you would need to find a way to mate up the 3-bolt housing to your 4-bolt manifold, have a custom DP made with the puck/lever built into the DP. The stock GN wastegate makes an immediate 90* bend right off the turbo and that will not work on a Z 3. Price out options 1 & 2 and compare the end cost to selling what you have and replacing it with a hybrid built to your specs. You might be surprised that option could end up being the best and least costly if you can get a decent price for your current turbo.

Mike, why don't you put the wheels on the backburner and focus on getting the car running? Pick up a set of Swastikas in the interim and you can always resell those when you are ready for the expensive wheels. How much of a rush are you in for a quality I/C? I might be able to help you there but we have to wait for Z-Gad to return from his long vacation. Drop me an email or PM or if you have time to spare or take a ride over to Orlando for a visit.

RB, L6, V-6, makes no difference to an SDS. 6 injs and 6 spark plug leads. The key is in the programming for the specific engine.

FYI, I went 11.10 with the stock Nissan IRS, R200, CVs AND drag radials. With that setup I cut a couple of 1.55s and ran consistent low-mid 1.60s. There was nothing trick about what I was doing unless you consider Tokico Illuminas trick. If the R230 was available with the ratio I needed I would still be running a Nissan IRS. Yes, I use a 200-4R and a t-brake, but for any Z-car trying to go quick, the trick is cutting good 60'. You cannot cut quick 60' times if you go to the track 2 times a year or use crappy tires. You need: - the proper suspension setup. 400lb road racing springs won't cut it - stop worrying about the Z-car squat and use it to your advantage - You must have at least DRs - practice, practice, practice - PRACTICE. Sorry if I sound irritated but I get so sick of hearing that a Z-car is not a good drag car, when there are several of us who are doing quite well. I also get irritated when I hear the turbo lag discussions. Sorry, I am done.

So, Ivan, you ready to kick ass and take names at Reynolds?

I have never taken an L28ET turbo apart so I do not know if the housing bolt pattern is the same. I am currently using a stock GN .63 housing that has been modified to fit a P-trim wheel. I also have a .83 GN housing also modified to fit a P-trim. My setup is from the 86-87 intercooled GNs. The 84-85 is a different animal with the turbo bolting up directly to the intake and no I/C. How can I help you? I have a .82 housing laying around. BTW, after working with GN turbos for a while, I took a good look at a stock L28ET turbo and was shocked by how small it is in comparison. I imagine if yu were able to use a stock GN .63 that the spoolup would be a little slower but I think the stock L28ET spoolup is too quick and somewhat useless when trying to launch the car. So, it might not introduce lag, it might just make it right .

Bernardd, a GN turbine housing uses 3 bolts not 4 like the stock L28ET.

Folks need to get over this "sports cars do not make good drag cars" way of thinking.

From the signature I would say I have a 1/8" border making it 1 5/8". It is a custom GN style DP. As you probably already know, try to see if all is aligned properly before you bolt it up.

Doug, I believe the hole in my .63 GN housing is about 1 3/8" and I am running 24-25psi. 1.25" should help your flow quite a bit.

Anyone who wants to try out the formula can download the spreadsheet and play with it. Obviously you need Microsoft Excel and a timeslip. Plug in your 60', 330' 660' and 1000' values in cells F11-F14. It will generate new values in the "Y=" formula in the shaded area. Put the value of the 2 coefficients in cells B11 and B12 and it will generate the 0-60 time in cell B14. Before you use it, look at the example and remember not to input in the red cells. http://www.turbobuicks.com/members/scottiegnz/accel060.xls

Maybe I did ot make my myself clear enough. I said nothing about comparing 0-60 to a 1/4-mile. By inputting your 60', 300' and 1/8 times, the fomula plots an acceleration curve which then determines the 60mph point on that curve. I have seen some on the web that ask for just the 60' time and that puzzles me because the average car is no where close to 60mp at the 60' mark so they are taking an educated guess at what happens beyond the 60' mark. I hit about 42mph at the 60' but things could happen to make the 60mph time not so predictable. The reason why the formula uses times up to the 1/8-mile to take into account all the variances. It does not go beyond the 1/8-mile because acceleraion starts falling off. As for the comparison I mentioned, Jeff is dead on. Just like a G-tech, my datalogger records time/speed/distance. Many of the formulas on the web are very good at their projections. Here is one of my favorites: http://www.prestage.com/Car+Math/ET+and+Horsepower+Calculators/Calculate+ET+and+MPH+using+HP+and+Weight+/default.aspx I plugged in 2750lbs and 488rwhp and here is what it projected compared to what the car actually ran in parens: ET - 10.36 (10.36) MPH - 131.57 (131.75) 1/8 - 6.60 (6.62) 1/8 MPH - 106.27 (104.34) Now, here is a perfect example of why I do not like most formulas on the web that take only a single input. This one estimates 0-60 by using your 1/8 ET and MPH. In my case it said 2.19. You can input your 0-60 time for it to estimate you 1/4-mile and the my result was 8.548!! http://www.tweak3d.net/videos/calcs.shtml

Yup, that's Chris Chow, well known in the Buick community and probably one of many in his stable. That's a special-built 394ci with 90mm turbos and a MOTEC. That was a pretty decent HP number. I am going to see if I can get my buudy here in Orlando to bring his GN up to Reynolds for some exhibition runs. It is an NHRA legal SS/DX car, 3600lbs, TT stageII destroked to 3.5L and restricted to 46mm turbos!!! It runs 8.30 @ 160+ in class trim and that factors out to about 1200rwhp. Maybe he will swap out the turbos and put it in exhibition/kill mode for us. He has been talking about doing that to see if it can get a 7.9x. BTW, another SS/DX GN just became the 1st SS car in the 7s. He is running a special-built Kenny Duttweiler 207ci TT stageII.

Let me start off by saying if the R230 was available with a ratio of around 3.00:1, that is probably what I would be running today. Let me help clarify some confusion about gear ratios and why I run such a low-numerical ratio and the C4 IRS. A few of you hit on some of the points but let me tie it all together. As Drax said, typically drag racers run a higher numerical ratio to go quicker but that does not necessarily apply to turbo cars, especially turbo cars that make monster torque down low. DavyZ pointed out that the higher numerical ratio increases torque multiplication but that is not something a torque monster needs coming off the line. The lower numerical ratio will not hurt a high-torque turbo drag car off the line and turbo cars will perform better when given the chance to build boost not rev quickly through the gears. With turbo drag cars there is a tendency to think more about lag off the line than to think torque. However, a well setup turbo engine is probably going to have a peak torque of at least 40-50% more than an equivalent size NA and in my case I estimate between 550-575 lb/ft at low RPMs. Keep in mind that with forced induction, for every 1bar of boost, the engine is capable of doubling the volume of intake charge it can pack into its cylinder. IOW, a L28ET at 14.7psi is capable of ingesting 5.6L of intake charge into its 2.8L displacement. That makes for a big bang and helps explain why a turboZ running boost in the teens performs equally with a V-8 Z. With an upper rev limit of about 5500+ and a .67:1 OD ratio, shifting into OD had too steep a drop-off in RPMs and hurt top-end acceleration. I had to find a ratio that would keep the car in 3rd gear when I cross the line at 130+. I costed out solving this with an R200 and needed a LSD, NISMO 3.0x R&P, R&P swapout, special axles (ask Stony how much his cost). An alternative was a SupraTT IRS with a 3.15 or the C4 with a 3.08. By luck, I landed the C4 cheap and then it turned into an engineering exercise . Will a Z handle better with C4 IRS than with a stock IRS? I certainly would not make that swap just to get better handling. The Z IRS is proven in competition and the Z/C4 IRS setup is getting into dark territory. Personally I think my setup has the potential to handle better, what with camber, toe and bumpsteer adjustments, plus I replaced the C4 monoleaf spring and tube shock with a coilover/adj shocks that mount in the stock strut housing. However, I am obsessed with drag racing the Z and never have and probably will not explore that avenue. When I want to "carve canyons", I drive the other car. So why did I make all those mods? I just would not have done it any other way . So, unless you have special gearing needs like I did or just want to delve into pioneering engineering exercises, you probably do not want or need a C4 IRS. BTW, to emphasize the point about lower numerical ratios and its effect on drag turbo cars, ponder this. I started the GNZ with a 3.90, then went to a 3.70, 3.54, 3.36 and now 3.08. The car now cuts mid-140s 60' and goes through the traps at about 132mph @ 5500+. So even with the 3.08 I am up against the same problem I started out with. I will end up going to a slightly taller tire (have 26.1" now) and you can bet the car will be quicker and faster and the icing on the cake, GET BETTER GAS MILEAGE!.

If you have a timeslip with 60', 330' and 1/8-mile times, I have a calculus-based formula that plots an acceleration curve and determines 0-60. Pretty damn accurate as it matches my datalogger with 100ths of a sec.

Well done, Dan.

Now imagine adding a turbo :D

This cruiser recently hit the drag strip and with a 0 boost launch, 20psi boost and DRs, it ripped off a 11.62 @ 120.92.

I guess you could take it as a compliment Happened to me last year also.

How critical is the inner fenderwell to chassis stiffness? I want to remove the equivalent of 6"x6" piece of the inner drivers side fenderwell. The metal would be removed where the fenderwell meets the frame rail just behind radiator support. I would also be removing a lot of the sheet metal from the radiator support, down low between the radiator and the HL. TIA and would appreciate no guessing or speculation.

From the last SEZs event at Reynolds. This URL allows you to play it online: http://www.misred.com/video/Scottie_10.36.ram If you want to download it, use this: http://www.misred.com/video/Scottie_10.36.rm BTW, you will need Real Player.