KCvetteowner

Correct me if I'm wrong here......
Twin-turbos were only available up to 1991 and in 1992 the engine became a "supernatural". With that said, how do the two stack up in performance (1/4 mile, 0-60, rolling 70mph romp), handling and comfort?


Can a Callaway be a "perfect weather" daily driver? I'd never want to drive one in the rain.

Thanks in advance!!!!

Stan A

Let's start at the beginning. Understanding the differences between the cars setup will you understand the performance numbers and handling limitations.

TW-TURBO horsepower-Torque 0-60mph 60-100mph
1987 345hp - 486lbs-torque 4.6 sec 5.8 sec
1988 382hp - 562lbs-torque 4.6 sec 5.5 sec
Dual Exhaust edition 435hp - 600lbs-torque 4.4 sec 5.0 sec
1989 382hp - 562lbs-torque 4.6 sec 5.5 sec
1990-91 405hp - 582lbs-torque 4.5 sec 5.4 sec
Supernat'l
1992-96 404hp - 412lbs-torque 4.6 sec 5.6 sec
1992-96 435hp - 425lbs-torque 4.5 sec 5.6 sec
1992-96 450hp - 445lbs-torque 4.4 sec 5.4 sec

The above numbers are averages for each model. The 1987 TT produced 345hp but still managed a respectable 0-60mph because of the small turbochargers used (less lag). The turbo car has better mid range performance to top end vs the Supernatural model. In 1988 Callaway produced the first 60+ cars with his special dual exhaust system which was never certified by EPA. A recall was issued and a standard Corvette exhaust was used as a replacement. Only 8 cars did not make the change over. These cars proved to produce more power and be better performers in all test categories. One 1988 convertible even was built with the sledgehammer cam. It was latter used to promote the Callaway name at most southeast car shows (estimated 530hp/700lbs torque). This car was latter updated to push the 600+hp/800lbs-torque mark.

Callaway cars both types are very reliable. Small modifications like rear axle changes or boost levels increases or both will produce a street car that will performance with the world's best exotics.

The number of showroom quality cars that are still on the road today is small by comparisions to total production number. Estimates of less than 330 tw-turbos are still on the road today (compared to the original 498 cars produced) There are more Supernatural models and 1990-91 Tw-Turbos available in showroom conditions as comparing them to the earlier models (1987-1989). The total number of Supernatural cars made is estimated to be between 250 and 400 units. They are no actual records to cross check.

As to the ability to be daily driver, the Supernatural is a little better suited. Although the tw-turbo will do nicely too.

Stan A
Director (1987-1999)
Callaway Registry Service

David-F

Stan you are the man! Only you could have answered this one correctly!

David Fulcher

bill mcdonald

That is great info Stan.

Question though, Was there ever a 450 hp Twin turbo car?
I thought I read somewhere there was a 450 hp version, for some reason I think it an option for speedster cars. :confused:

callaway95

I only drove a TT once, an '88 model with over 100K miles on it, but the torque was still mighty impressive. Without owning a TT, I can't really comment on reliability, other than the fact that the amount of extra plumbing is obvious......... but have not heard of any horror stories.

The Supernatural I have is very driveable, and with the exception of the more noticable exhaust note, routine driving is virtually unchanged. The idle is smooth and I have had no real problems....... I've had a slight performance issue lately, but I'm working through it.... some of the ponies seem to have left the stable this past spring, but I'm getting close to having them back. I've yet to witness a later model TT at the track, so I can't tell how my NA car would compare........ The only TT I've seen run was an '87, which on a very hot day ran a 13.9 @ 102 ; on the same day, I ran a 12.6 @ 113.......I have many road test back issues, which have the TT's running anywhere from mid-12's to mid 13's @ 107 to 113 mph....

Dave

Stan A

Hi Bill,

The 10 Speedsters built were powered by the TT system which produced 450hp/600ft-lbs torque. Another Speedster was built later on a ZR1 platform (Supernatural package). Your standard TT package can produce this same power by simply raising the boost from 10lbs stock to 12.5lbs with no harmful effects. A good example of street power that is reliable is taking a 1989 TT with a 3.54 rear axle setup and adding a "free-flow" exhaust, raise the boost to 12.5lbs, rework the intake slightly (cleaning & port matching),change to larger injectors, raise the fuel pressure. You will push over 500hp easily raise the torque to 650+lbs-ft and find that you will have almost no competition in straight line performance runs. This includes "rolling runs" too. 0-60mph times will fail into the low 4 sec range and 60-100mph will hit the mid 4 sec range. We are talking 0-100mph in the mid 8 sec range. This is F40, F50, Diablo times for about 20% the cost. All of this and you still can make a causal run to the local 7-11 for milk.

Callaway's middle name is reliabilty. All his car will hold up under normal operations and even when put under so-call "performance load" they still hold up. As to maintenance, they require nothing extra over the normal tune port model (except for a quart and half of extra oil--15w-50w only). However, it is suggested that you warm up the turbo housings/oil before engaging the turbo boost to about 150 degrees. Also to let the same cool down before you turn off the motor. Let it idle for about a minute or so especially after heavy turbo use. This will protect all turbo components from the high side heat.

The ultimate TT Callaway car is the 1994 ZR1 Supernatural Tw-Turbo. Producing 782hp/682lbs-ft torque. This car had a complete transformation. Updates with all mechincal components (tranny,drive shift, radiator, coolant assembly, and much more). The cost for the 6 speed ZF conversion was $6,000 by itself. This car cost $250,000+. Nothing can touch this car with performance and reliability. People say that the LPE twin turbo ZR1 is faster, however, this car is limited to the boost already being used. 1994 ZR1 TT is running just 12.7lbs boost and can run upwards of 20lbs+ safely and reliable. We are talking over well over 1000hp+. To the best of my knowledge there is no car that can match this that is "streetable" as a daily driver. By the way it is for sale for 140k or so.

Rarity makes the Callaway TT a good value car to buy. However, I would expect to make any money if you buy one. This is the "most misunderstood" production Corvette ever built. One day in the very near future this model and all its applications will spring to the front as one of the hotest Corvette to own for a true collector.

This car does require some driving skills that the average Corvette owner may not have (but can develop). Understanding the power and torque ranges with regards to the rpm and the proper shift points is the real key to the full potential of these cars.

Stan A

SCVette

Callaway TTs are very reliable but their rarity and collectability make it hard for me to drive them daily. My '88 convertible is as clean and original as the day it was converted with no problems with drivability. The few problems I have had with my '90 aerobody coupe have to do with heat soaked (cracked) oil lines for the oil cooler. The underhood temperatures from the turbos are brutal on hardware and hoses. With basic maintainence there should be no problem with driving (in clear weather) daily.
I have been considering increasing the amount of boost to 12lbs and now after this thread I think Im going to do it.
Taylor

Stan A

Hi Taylor,
Having two Callaway must give you lots of hours of driving fun.
You mentioned the heat problem with the 90 aerobody from the oil cooler assembly. The aerobody facsa is more closed in than the stock facsa. For this reason it will hold in more heat. I suggest you move the horn assemblies from their current position. This will open up a direct patch to the front side bottom and allow more hoot air to be drawn out and some outside air under the hood.
The hoses you spoke of need replacing. I would also shield him with heat wrap or metal sleeves before reinstalling.

Raising the boost to between 12lbs & 13lbs must be done carefully. The system works with turn screws (spring loaded) located on the side of each turbo. Be careful and not strip or over loosen these control screws. Start by marking a starting point on the side of each screw (white out will work fine). Use this mark as guide and turn each counter clock wise two complete turns. Test the car by running it at full boost. If you find that it has not move to the goal level of boost, turn it two more time and repeat the check. Be careful it will be really hot under there. Do this until you reach the designated boost. Be sure and check the enrichment injectors and be sure they are both working. Electrical test on each one here will tell if there is a flow. Also raise the fuel pressure to between 46lbs to 48lbs. Also check your cap and rotor and replace if needed. You may want to check your spark plug wires for cracks and breaks.

This can be done on your 1988 cars too. Any improvement on your exhaust flow will be felt in a big way. Better high flow cats can be purchased that will do the trick. Just another way to build power.

Power loose under high engine heat conditions can be improved by replacing your current radiator with a high flow unit and remember to install a high flow water pump too. These items can be find in Eckeler's magazine. If you are interested in power loose and gains by temperature controls, email me directly.

Just a few tips...............

Good luck,
Stan A :D

notbob

What do you do for a living to have all those cars?

I've got 1 daily driver & 1 vette and it's killing me on costs..

SCVette

Thanks Stan,
The counter clockwise turning of the wastegate adjusters is just what I was looking for. I have recently installed a digital MSD 6+ ignition, MSD blaster coil, cap, rotor, MSD 8.5mm wires, and Sean Roe Air/Fuel ratio meter. I've been restoring/upgrading parts on the car like the steel braided hoses for the oil lines but I was noticing some of the other lines(oil and water) feeding the turbos are starting to look pretty bad. Probably good winter projects along with the ceramic coating of my headers.
As a performance cooling question, how is the throttle body water heating system bypassed? Is there a kit for L98s that bypasses the heated water without getting in the way of the rams horn intake system?

Hey notbob,
We write and market internet commerce software. Things were pretty good last year(when I got both Callaways), now it is a matter of finding time to work on and drive them each 3000 miles/year.(Collector car insurance milage limit)

90Callaway

Hey Stan! Where have you been? I was wondering... haven't seen you post for a while. :seeya

Stan A

The by-Pass kit I believe is available from Eckeler's or Mid America. If you plan to drive your car in the winter when temperatures are in the low 30's or 40's, I suggest that you not use the By-Pass kit.

The space is less under the enrichment horn (injectors units)to work with than with the standard connection line. Take your time and do it right so as to avoid any coolant leaks.

Hi Callaway90,

Been real busy with family related problems over the past few months. Had little time to do anything else. Nothing is really new except Shane is selling the Registry car. It looks like it rolled off the showroom display. Whoever buys this will get one fast accelerating beast along with new car looks!

I will keep intouch... E-mail directly when you have time. I have something to tell you about.

Take care All,
Stan A

:chevy

notbob

Hey SCVette,

Do you need anymore Web Developers? It's what I do for a living, I also do some DBA work & Systems Administration.

Thanks,
Bob