Hey Guys,

This might actually be my first post after a year of "listening". Anyway, I had a rear-mount T70 and intercooler setup running 5.5lbs installed in my '97 Z-28 A4. The builder is a very reputible Vette builder in Denver and led me to turbo rather than an engine build. My problem is that the numbers aren't hitting where he said they would and the ETs are terrible.

It dynoed 365RWHP and 450RWTQ with one Walbro 255 pump and 42lb injectors. He thinks it needs another 255 to keep the pressure up and started installing it without approving the cost. I had him stop so it's not complete yet. He says that 400-425RWHP will be possible without a doubt after the other system is in place.

Now, the real issue. I wanted a fast 1/4 mile car and he knew it. I ran last night (at ~6,000 feet) with aweful times. My best stock run was 14.991 at 91MPH. My new best is 14.839 at 101MPH! Much better trap speed but no improvement in the ET. The 60' are .3 slower due to the turbo restriction even leaving at 2000RPM.

Basically, he wants to finish the fuel system, add a 75HP nitrous kit for launching and cooling the air (in place of the water injection) and go to 9lbs of boost. He thinks that's the limit of the stock motor and should run 12.5 at altitude.

Should I continue with this or just enjoy the awesome high-end I'm getting and live with it for awhile? Is his solution going to shave 2.5 seconds?

Thanks in advance guys,
Dave

 

POWER BRAKE THAT SUCKER!!!!!

You should be able to knock off a nice chunk of time if you line up and slam the brake and push the gas down as far as you can without the car moving. This might take some practice before you go to the track, but if you can pre-spool the turbo it will lauch hard.

The other thing I would do is to turn up the boost. 8psi should be fine on an intercooled setup with the stock stuff, especially if you are running it at 6000+ altitude.

You should be fine with the single walbro for now. The tq and hp numbers look like they should, 450rwtp is alot with a stock engine. I think if you can prespool the turbo you'll see the times come down alot, you also might want to think about a higher stall converter. For $500 it will make a huge difference in the launches and with the higher rpm the turbo will spool in half the time. I would go with a 2200-2500rpm stall for a daily driver, it will help your setup out alot.

 

9psi on a stock LT1 = boom. It may live for a week, or it may live for 5 minutes, but 9psi is too much for the LT1 pistons. Get your fuel system up to par and enjoy what you have while you build a new shortblock to handle more boost.

Just my $.02

 

>even intercooled boost?

but if you use a power adder your going to rebuild eventually!

 

They had the same problem with the Thunder Racing STS car. It actually ran a slower et with the STS, but with 100 more rwhp. With a converter swap, it dropped a whole lot more, though.

Mike

 

A couple of things to consider. 1. Don't know what your fuel pressures were
but did your mechanic mention it? Were you actually dropping pressure where you really require a second pump? 2. Nitrous is not an intercooler. In short, using nitrous will boost your HP but you're more likely to detonate. 9 psi on a stock motor with nitrous -- better set aside money for a rebuild. 8 psi alone is about max on a stock LT1 using an intercooler.

 

 

Sounds like he doesn't know what he's talking about. I have a Vortech S-trim running about 6-7lbs of boost, a vigilante 2800 stall, 1 (one) walbro 255lph fuel pump, 36lb injectors, and am running 12.1-12.3@110-113 at a DA of about 4000 feet. Don't know the hp #s, but guessing somewhere around 410rwhp/450rwtq. I'd say get a stall and be done with it, you should have enough fuel.

 

Thats because Angie's tranny was junk I believe. They posted her new numbers with rebuilt tranny and the same low boost (6 or 8psi I believe) and she runs bottom 11's now. The post was on ls1tech.

For the original posted, a T70 STS is too big for your mild engine. A T60 would have been best for you. What a/r turbine housing do you have? Get a .68 if you dont have it already. That will help spool and wrap the y-pipe to the turbo...it will help spool.

 

The impression I got talking to her was that it was strictly a converter problem. I thought the car had run low 12's on motor, then high 12's at much higher mph with the turbo. They put in a Vigilante turbo converter and now it runs low 11's at 120. Could be wrong though. . .

Mike

 

Here ya go Mike, they said they replaced the converter and fixed the slipping tranny:

http://www.thunderracing.com/project...n=read&pgid=92

 

im not impressed with the rear mount..i smoked a 95 sts Z28 with my supra on 18psi....bad

 

Well I think you have no traction personaly. That is what I think your problem is.

My car stock ran a 14.97 at a lil over 91 mph at a DA of 6780 or so. Im up in Casper, Wyoming. Ran it in Douglas a lil bit ago.

With my front mount turbo im looking for a lot of gain. Traction was an issue the day I raced (even on slicks) so im assuming I will have a similar problem as you.

A single 255 should be plenty of a fuel pump for what you are doing.

And with turbos, on average the normal stall speed is normaly DOUBLED. So you should be able to leave a lil higher than that 2000 rpm. Make sure you have traction. 13's are in your future. You jsut need to get some slicks and stall that baby up. The extra fuel pump is wasted money IMO. Your mech is out to make some money IMHO.

 

Your dyno numbers are somewhat inflated based on your trap speeds here (I take it you ran at bandimere). My 95 bolt on LT1 has run 14.5@99 mph, with 309rwhp (corrected) on a dynojet. Assuming your dyno numbers are corrected.. even if it was on a Mustang dyno, you're not much over 300rwhp actual. You should in no shape or form need another walbro, even if it is a turbo car.


I dont think you're going to get to 12.5, at least not with a stock converter and drivetrain. I know of a stock motor LT1 with a Procharger (auto car, stall, 3.23s, slicks) running about 9 psi of boost (equivalent of 6 psi at sea level).. and that car dipped into the high 12s.

I am kind of surprised from your loss in ET and a slower 60 foot time. that sucks.

 

Wow, that was the wide range of input I was looking for. I know the engine will need mods too but this was stage 1 for my budget.

*The HP and TQ numbers seem accurate to me. It pulls well once the turbo hits, it just takes forever to get there.

*He agreed that the T70 was more than it needed but I wanted an upgrade path without replacing new parts (like the turbo unit).

Traction doesn't seem to be an issue other than at the line (power braking 'till they spin). On the track it won't even break between gears. I do have the M/T drag radials that weren't on the car. Maybe I'll try the tires and a higher RPM at the line for starters. Will the transmission and torque converter hold up to those launches? Maybe spend the $500 for the 2500RPM converter too? Should I look at a specific brand?

Thanks again guys,
Dave