Scottie-GNZ Posted April 5, 2003 Share Posted April 5, 2003 I currently run 26x9x16 QTPs on Z-28 16x8 wheels and was looking at getting a tire that hooked better when these wear out (close). I was thinking of switching to 15s if they cleared my brakes, because the 16s have limited or no choice of other tire sizes. 5-lug 15x8 Welds w/5.5" BS are fairly easy to find especially on the Mustang boards. I have to run 15psi in the tires because anything less and the car gets nervous on the top-end. Launching with more than 12psi boost makes the car come out so hard, it simply annihilates the tires. I started experimenting with my chip (limited programmability) to run the leanest setting to get the quickest 1/8-mile. That, of course, would be too lean for the top-end so I installed a nitrous fuel solenoid as a 7th with a very small jet and intend to turn it on about 1-2 secs after 3rd-gear LU (7-8 secs into the pass). The LU and solenoid will both be controlled with home-made electronics, thanks to Rick Bowers (SPEEDER). Well, the experiment seems to be working because a 12psi launch last night simply destroyed the tires and even backing off a tad made little difference up to the 330' mark when I got out of it completely. Our local track does minimal prep for T&T nights but normally I get little or no wheelspin at all. When I made the U-turn for the return road, it sounded like all hell had broken loose back there. I took a quick glance expecting to see the halfshafts hanging but they were connected solid. I jacked it up and the u-joints and halfshafts are fine so I am sure it is the diff. At first it made loud metallic sounds like a broken driveshaft or axle flopping around, but only in a turn. That noise then went away and now I get a LOUD, heavy squeal when I turn in either direction. I think I broke the spider gears and the LSD. Drives perfectly normally going straight and I made it home with no problems. Ironically, the car has cut several 1.40s with several 1.45s, so wanting to go quicker might be a little greedy, but I know the car can do it because the 1.40s seemed so effortless with 10-12psi launches. Looks like I will be down for a while, but I guess I have to expect that trying to run the way I do with a street setup Quote Link to comment Share on other sites More sharing options...
BRAD D Posted April 5, 2003 Share Posted April 5, 2003 Ouch, So how hard will it be to find some new parts for that diff? Is there a lot of aftermarket LSD's you can use? But on the other hand 1.40s wow, with that 60' time what would your 1/4 be? Quote Link to comment Share on other sites More sharing options...
BLKMGK Posted April 5, 2003 Share Posted April 5, 2003 Kripes, the launch must feel incredible! Lifting the front tires yet? Hope you've got your head against the headrest when that sucker comes out of the hole! Hope you can swap that out easily and that nothing custom got mangled. Quote Link to comment Share on other sites More sharing options...
Scottie-GNZ Posted April 5, 2003 Author Share Posted April 5, 2003 with that 60' time what would your 1/4 be? The best 1/4-mile IS 10.36 @ 131.7 and that was at the last Z meet and with only a 1.49 60'. What I mean is if you want to speculate and say the 60' was 1.45, it could have gone 10.30. Won't know how bad itis until I pull the diff but pretty much everything I would need is available. A DANA44 to replace it would be sweet, but the DANA44 with a 3.07 is not common and folks are commanding 4-figures for a DANA44 chunk It hits hard with the t-brake but with the 5-pt harness tight and the helmet on the headrest, it is not a big shock to the body BUT you had better be focused! Ironically, looking at the video, it does not look like it. Tough to lift the front wheels on an IRS but the front-end is fully extended. With real slicks and a 18psi launch it should do it Quote Link to comment Share on other sites More sharing options...
BLKMGK Posted April 6, 2003 Share Posted April 6, 2003 Do you think you'll need to goto an upgraded diff or can the type of diff you were using before be beefed? I know it's tough to lift a wheel with an IRS, only one Supra I know of has done it I figured with your lighter car it might have been easier. A 1.4 60ft is SICK! Quote Link to comment Share on other sites More sharing options...
BRAD D Posted April 6, 2003 Share Posted April 6, 2003 So with the times you are pulling, you should have around 475HP @ the wheels? Quote Link to comment Share on other sites More sharing options...
BLKMGK Posted April 6, 2003 Share Posted April 6, 2003 So with the times you are pulling, you should have around 475HP @ the wheels? Do you really think it's that low? Scottie, getting that thing on a dyno would actually be interesting. I'd love to see the shape of the powerband let alone the HP and TQ figures. Quote Link to comment Share on other sites More sharing options...
BRAD D Posted April 6, 2003 Share Posted April 6, 2003 I would like to see it on a dyno as well, it dose not take much hp to make a Z pull some fast times. How heavy is your car Scottie-GNZ? Quote Link to comment Share on other sites More sharing options...
Mudge Posted April 6, 2003 Share Posted April 6, 2003 Hard to say, a 470 RWHP Camaro can run a 10.8@130, either way its damn fast. Scottie, you were running the small automatic C4 rear? Quote Link to comment Share on other sites More sharing options...
Scottie-GNZ Posted April 6, 2003 Author Share Posted April 6, 2003 Yes, I run the "small" DANA36 but keep in mind that my car is probably 650-750lbs lighter. See my comment about the DANA44 above. My car weighs in at 2,750 w/me and the HP is 485rwhp based on the timeslip in the only formula I use. There are other formulas that register higher but the closest is the one on Prestage: http://www.prestage.com/carmath/calc_etmph.asp This is the only formula that I use as I want consistency in the measurment. However, realize that this is more of an average through a 1/4-mile and so the number will be lower than a dyno where you measure the highest peak HP. A turbo car will be putting out a little less HP in the lower gears because of the gear multiplication, not being under extreme load like on the top-end and you are accelerating from rest. Hard to say what it would be on a dyno as there is such a variance in how dynos calculate HP. I tried putting the car on a dyno once and it was a nightmare. The way the operator wanted me to bring the revs up and he applying the load did not sit well with my chip. Once the load was applied, the engine bogged down slightly and took the chip out of full-power mode. Not sure I will ever see a dyno as I feel I am doing fine tuning it on the track. I am able to go quicker with less HP because I am able to put the power down immediately and more effectively. 2 primary reasons are how well my suspension setup works (and we won't get into a squat discussion again) and I focus on optimizing the 1st 1/8-mile not the top-end. I run the big P-trim turbine wheel but with the tiny .63 housing for quicker spoolup. When I ran the big .82 housing the top-end was phenominal but the 60' was high-1.60s. Guess which combo produced the quickest ETs? The huge turbo(s) and injs that are great for the top-end hurt you at the line and the front-end of the 1/4-mile. I run the 1/8-mile in 6.62 and the 2nd 1/8-mile in 3.74 and the 60' time affects the ET by a factor of 1.5. So, where is there more opportunity for improvement? That is why I am experimenting with improving the 1/8-mile and you do that by leaning out the fuel as much as possible. I can get away with that because even though I am running 24.5psi all through the 1/4, the engine is under less load and demands less fuel. The trick is knowing when the fuel demands increases at the top-end and richening the mixture accordingly. No way to simulate and tune for that on a dyno. The key is caution, patience to take baby steps over several passes and effective use of the datalogger. Yikes, I am rambling again. Quote Link to comment Share on other sites More sharing options...
Mikelly Posted April 6, 2003 Share Posted April 6, 2003 Damn Scottie, You are my Hero! I predict if You keep on this path of measured calculations and aby steps, that you will eventually make it into the 9s... Remember guys... I said it first! Mike Quote Link to comment Share on other sites More sharing options...
Jeff Posted April 6, 2003 Share Posted April 6, 2003 Sorry to hear that it let go Scottie. That's awesome that you were able to limp it home though. Definetly sounds like the spider gears went on you. I will check with a friend who closed his Corvette shop not too long ago and see if he has a line on any Dana 36 chunks. Quote Link to comment Share on other sites More sharing options...
Guest zfan Posted April 6, 2003 Share Posted April 6, 2003 Scottie, Checked out the prestage program, it's pretty cool and very accurate from what I got back. Thanks! Mike Quote Link to comment Share on other sites More sharing options...
Mudge Posted April 6, 2003 Share Posted April 6, 2003 Yes, I run the "small" DANA36 but keep in mind that my car is probably 650-750lbs lighter. See my comment about the DANA44 above. Heck, I know, must be alot easier with so much less weight, equivalent to about 4 passengers... Quote Link to comment Share on other sites More sharing options...
BLKMGK Posted April 6, 2003 Share Posted April 6, 2003 Scottie - IF you could put the power down would you run more boost at the start or up top? I can adjust my boost vs vehicle speed. Right now I'm not doing it as I'm having some trouble controlling boost and some issues with the VSS sensor. My gut says run it higher up top but I'm not sure. I can also do an ignition retard up top if I wanted using VSS or a switch. Going to the track on the 30th so we'll see how it goes. I think you would love this ECU if you could ever decide to switch away from the OEM unit Quote Link to comment Share on other sites More sharing options...
speeder Posted April 7, 2003 Share Posted April 7, 2003 I too am an admirer of the Scottie science of drag racing. Feel free to ramble and educate the masses. Sorry to hear about the breakage. I also know a guy who is into Corvette parts- Will inquire if you want. Looks like a good time for kludge electronics upgrade during the downtime - I'll e-mail. Quote Link to comment Share on other sites More sharing options...
Scottie-GNZ Posted April 9, 2003 Author Share Posted April 9, 2003 Well, I pulled the diff tonight and expected to have gear chunks come falling out. SURPRISE, SURPRISE, not a damn thing wrong with the gears, even the spider gears. I am not able to see every single teeth on the spider gears but from what I can see, they are OK. Only thing left are the clutch packs. Cannot imagine that the loud banging sound I first heard when I made a turn was coming from the clutch packs. It sounded like a u-joint had broken and the axle was banging around back there. That sound eventually subsided and was replaced by a loud squeal when I make turns. Only conclusion I can draw is that the clutch packs came apart and eventually fused together or are binding : : So whats next? Was this just a case of a 19-yr old part that had seen better days and I finished it off? I will probably just rebuild this clutch pack and put a cap on making the car go faster or even backing off a tad while I decide the next step. I just cannot get myself to ante up 4-figures for a DANA44. Given that choice I would rather sell the current setup and go to a solid setup, big slicks, little more power out of the engine, lift the front wheels and run mid-9s. Intriguinely, since the power would be coming from a mild cam and more boost, the driveability and economy would not be hurt one bit. Hmmm. Somebody, Stop ME! :D Quote Link to comment Share on other sites More sharing options...
Guest zfan Posted April 9, 2003 Share Posted April 9, 2003 Sounds wicked Scottie, running Nines with the fronts to the moon! Very trick! Mike Quote Link to comment Share on other sites More sharing options...
Mikelly Posted April 9, 2003 Share Posted April 9, 2003 Well now I gotta ask... What do you plan to sell your rear setup for??? 'Cause I'm thinking... Ya Know, I could VERY easily sell ALL of my R230 stuff including both Diffs, the axles, the rear modified mustach bar, the stock R230 drive shaft, the custom aluminum brace, plus the R200 modified axles, the whole REAR setup under my car (Including coil overs and New Tokico struts and adjustable swaybar, adapters... Now SOMEBODY STOP ME!!! Let me know Scottie! Mike Quote Link to comment Share on other sites More sharing options...
Guest thepenguin99 Posted April 9, 2003 Share Posted April 9, 2003 Hmm I know a guy who would buy a complete r230 setup with coilovers and adjustable swaybars if one came up for sale.... I think his handle is thepenguin99 and goes by the name of Nathan =). hehehe Nathan Quote Link to comment Share on other sites More sharing options...
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