Stock engine block.
Stock crank.
Stock rods.
Stock pistons.
ARP bolts.
CompCams 12-404-04 cam (LSA 114, duration 222/225 @0.050, lift 0.464/0.464
CompCams 858-16 Pro magnum Hydraulic lifters
CompCams 1412-16 magnum roller rocker arms
AFR 190 heads with 74cc chamber size.
Holley Stealth Ram that I modified to clear the stock hood.
Haltech E6K
120 lbs injectors.
SX fuel pressure regulator.
Twin BOSCH fuel pumps and a surge tank in the rear right fender.
Dana44
4L80E controlled by a TCI T-Com
Vigilante converter
Front mount XS Power intercooler with 24"x12"x4" core.
HKS 'style' 50mm wastegate
Garrett GT4288N turbo from a Volvo semi truck
E85 ethanol fuel.

It is not a stock engine, but the short block is stock except for ARP bolts.

The 1984 Corvette has the CrossFire Engine.
The stock engine was rated 205 hp @ 4200 RPM and 290 lbs-ft @ 2800 RPM.

ahhhh...
Very nice.
You're throwing some really good numbers.
Amazing work.
:cheers:

E85 :cool:

I've been having the same problem with mine on keeping high boost at high rpm. It hits a max and then drops off.

I am going to do a test on mine.

I an going to put a manual valve on the other boost port on the wastegate. If a manually apply boost on that port at 5000 RPM and see a boost increase, then it is a wastegate related problem.

Both boost pressure and exhaust pressure try to force the wastegate open and balance the spring force. If exhaust pressure increases with rpm, then the required boost pressure required to open the wastegare decreases with rpm. By applying boost to the other port I can force the wastate to close if it is open.

If that works then the boost drop can be solved with an electronic boost controller.

If that does not help then the turbo is too small.

Joby,

Here's another couple of test that I tried.

1.) Do a hard run starting from a low rpm and work your way to redline. This should give you a boost/rpm curve. Now try to down shift to something 1-2k from redline. Does the boost get to be higher than were it was at that rpm on the boost/rpm curve? I believe that this thing is caused because the exhaust pressure doens't have time to build up and pop open the wastegate.

2.) If you have an adjustable wastegate spring and a ball and spring boost controller, then by tightening the wastegate spring you should see an improvement, even if you do not adjust the boost controller.

I've been looking at new electronic boost controllers, but the ones that will hold the wastegate closed are a bit expensive. I'll probably be doing that this winter along with all of my other mods that I'm planning.

This a 'standard' boost controller setup.

http://s2central.net/images/boost_control.jpg

By adding another identical valve to the top wastegate port and inverting the duty cycle signal to that valve (Simple transistor) a simple controller force the wastegate to both open and close.

0% duty cycle will apply full boost in the top chamber and atmospheric pressure below.
100% duty cycle will apply full boost in the bottom chamber and atmospheric pressure above.

This is out of the instruction manual of the one I was going to get. I hope I didn't break any copywrite laws. :D

I don't know of the control is actually pwm'ed or not, but from what I've read it works well. The air pressure goes strictly to the top of the wastegate until it needs to open the gate, then it puts some to the bottom to open the valve.

http://i229.photobucket.com/albums/e...tte/eboost.jpg

A comparison between the Garrett GT4288N that I used last summer and my new Garrett TBP7501.


http://www.joby.se/turbo/gt4288n_vs_...N_DSC00158.JPG

http://www.joby.se/turbo/gt4288n_vs_...N_DSC00160.JPG

http://www.joby.se/turbo/gt4288n_vs_...N_DSC00163.JPG

I thought that it was tight before but I was wrong ... With the new turbo it's tight but the hood still closes.

http://www.joby.se/corvette/mods/200...N_DSC00142.JPG

http://www.joby.se/corvette/mods/200...N_DSC00143.JPG

http://www.joby.se/corvette/mods/200...N_DSC00145.JPG

http://www.joby.se/corvette/mods/200...N_DSC00146.JPG

http://www.joby.se/corvette/mods/200...N_DSC00147.JPG

http://www.joby.se/corvette/mods/200...N_DSC00148.JPG

http://www.joby.se/corvette/mods/200...N_DSC00149.JPG

http://www.joby.se/corvette/mods/200...N_DSC00150.JPG

I made a fixture for the new flange. The next step is to cut the old turbo flange off the header and weld the new flange to it.

What are your expectations for the new turbo? I remember seeing your videos, can't wait to see your next videos with that monster on it. :thumbs:

Boost peaked at almost 20psi before 4000 rpm.
At 5000 rpm boost was down to 13 psi with an exhaust pressure of 43 psi. It is probably 150+ hp lost from exhaust pressure alone.

I maxed out the turbo (both compressor and turbine) at 4000 rpm and I want move that up to at least 5500 rpm.

With the new turbo I want to make more power with less boost.

where did your old turbo come from? a volvo truck? was it diesel?

The Garrett GT4288N is used on the Volvo D10A engine.
It is a 264kw (354 hp) 10 liter (610 cui) diesel used in Volvo Busses and Volvo FL10 semi truck.

:lurk:

Not much news yet.

I cut the old flange off the header and that's about it.

http://www.joby.se/corvette/mods/200...N_DSC00228.JPG

http://www.joby.se/corvette/mods/200...N_DSC00229.JPG

http://www.joby.se/corvette/mods/200...N_DSC00231.JPG

This is a great thread. I just picked up a 86 L98 with aluminum heads.. I've had three turbo cars. I plan to turbo My vet with me doing all the mods.
Joby could u have used ur stock headers for the fabrication? Or will they put the bend to close to the ground?

I also have a Garret turbo off a semi truck that I plan to use. Friend has a 80 vet carbed with diesal truck turbo an his car ran 6.7 in 8th mile. Stock motor!

I could have used the stock exhaust on the drivers side. It would have been too tight on the passenger side.

More pictures ...

http://www.joby.se/corvette/mods/200...N_DSC00470.JPG

http://www.joby.se/corvette/mods/200...N_DSC00471.JPG

http://www.joby.se/corvette/mods/200...N_DSC00472.JPG