The soft mount thats usually bolted to an fbody k-member is bolted to the engine, and they use long *** k-member mounts like a 4thgen.

-- Joe

 

4th gens have another set of bosses on the block (LT1) or a completely different location for them using different mounts (LS1), in both cases putting the mounts further forward, which would easily clear most vette exhausts, but since traditional SBC’s don’t have those… are you saying that the mounts are long as in front to back or up and down?

 

You see the engine mounts in these pictures:

 

I think that it is time for an update.

I ran the Corvette without turbo the last summer and I had one problem after another. I had some fuel problems and rewired to semi-sequencial injection. (The injectors fires i pairs) I lost spark and installed a MSD 6AL and converted to crank trigger. When I finally was ready to install the turbo the tranny started acting up with black oil.

I went to the dyno anyway to get a pre turbo run and that killed the tranny for good. I only managed to get one good run on the dyno with 230 rwhp.



After that I parked the Corvette for the winter.

It was the converter that had a major failure. The oil cooler and transmission was full of aluminum shavings.

I bought a new 9.5" Vigilante converter with a 3-disc lock-up.

I finished the turbo installation and started the Corvette early july.







I was running 10 psi boost and I had major traction problems at lower speeds.

I went to a local racetrack on the 11/7.
This is a picture from the 'pacecar' lap before we could have some full speed runs around the track.



This is a short movie. I am having some traction problems coming out onto the straight.

 

On 25/7 I went to a test and tune day on a airstrip and ran three times with similar results.

On one of the runs I lined up against a Chevelle with a cage, real big tires and a 720+ hp 572 cui crate engine.

The chevelle ran a 11.508 sec ET @ 121 mph with a 60' of 2.163 sec.

My best was 13.459 sec ET @ 118 mph with a 60' of 2.561 sec making tiresmoke forever.
----------
On 9/9 I drove the Corvette over 110 miles (one way) to another test and tune avent. It was my only chanse to test my new Hoosier Drag Radials (dot) before the winter.

First run with 18 psi in the tires.
60" 1.82 sec, ET 11.24 sec med 122 mph trap speed.

I went from mid 13 to low 11 with only new tires!!!

Second run with 14 psi in the tires.
60" 1.72 sec, ET 11.14 sec med 126.6 mph trap speed.

Third run was another 11.14 sec.

I ran three more runs but no more ET improvement.
I got my best trap speed on the 5th run. With a better 60" that could have been a high 10.
60" 2.04 sec, ET 11.45 sek, 131 mph trap speed.

It is not every day you improve you personal best with over 2.3 seconds.

 

On 18/9 I went to the dyno shop.

Before I went there I activated lockup in the converter during WOT and I felt a major differance. It became another animal when the tranny shifted to third an engaged the lockup. Bofore this the engine never was below 5000 rpm during wot.

At the dyno shop I got a major shock looking at the tourqe curve.

627 rwhp at 4200 rpm.
1086 Nm ( 801 lbs-ft ) at 4000 rpm.



It does not hold boost at higher RPM. Peak boost is 1.3 bar (19psi) at 3900 rpm and drops to 0.9 bar (13psi) at 5000 rpm



I need a bigger turbo ... it is DONE at 4000 rpm ...

I measured exhaust pressure before the turbo after the dyno run and it was way over 40 psi at 5000 rpm.

 

Stock engine block.
Stock crank.
Stock rods.
Stock pistons.
ARP bolts.
CompCams 12-404-04 cam (LSA 114, duration 222/226 @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.

 

wow, some amazing results with that tiny turbo. a t-70 would do lots more for your setup for under $600. 50 psi backpressure yikes!! thats 2.5X the boost its making, deffinately a restriction! Hope you get everything

 

He posted that he is already running a "new" series T-70 in the post above your response.

 

What size turbine do you have on that GT4288? Is that a typo and supposed to be a GT4088 or a GT4294? With the EBP in the 2-2.5x range, I bet it would make more power with a smaller exhaust lobe. That CompCam seems like it would be about perfect for slightly less EBP.

Nice setup. It has all the parts for 10's in the 1/4 mile. Have you measured the PSI drop and IAT drop from the IC?

EDIT: Ignore the comment about the cam exhaust lobe. Poster edited the lobe size.

 

GT4288N , No typo.
I think that it is a GT42 with the same compressor as the GT4088.

Compressor:
Inducer 64.7mm
Exducer 88mm
A/R 0.72

Turbine:
Inducer 82mm (=GT42)
Exducer 67mm
A/R 1.22

Pictures of the turbo: http://www.joby.se/turbo/gt4288n/

I bought the cam when I was running the Vortech supercharger and it is a supercharger cam.

I am going to use another turbo. The problem is finding one that still fit under the hood without changing too much.

I have not measured the pressure or temperature drop over the intercooler.

 

wow i cant beleive that motor is holding over 600whp and 800lb ft torque on stock internals!!! you got to be kidding me!

 

Great info, great pics. With that exhaust wheel it sounds like you could replace that T4 housing with a T6 housing. That would bring the EBP down. Maybe keep an eye out for a GT4294 off of a diesel. Most I have seen are T6 1.28 A/R housings. It will probably require more fab work though.

I did some EBP measurements on a twin setup using two T3 .48 A/R housings on a stock 305ci. I have 2-2.5x EBP compared to intake boost. It builds boost at 1700 RPM so I am leaving it as is. What RPM do you see positive pressure at?

I wouldn't change that cam.

EDIT: The dyno curve looks like it starts making boost at 2800 RPM.

 

Impressive, as always........

Its fun to read about you guys up north... (JoBy, Kristian, Fredrik)

/N.

 

I already bought a GT4594 but I think the compressor inducer is a bit on the small side. The exhaust side is much bigger than the GT4288.

Compressor:
Inducer 63 mm
Exducer 94 mm
A/R 0.66

Turbine:
Inducer 87 mm
Exducer 78 mm
A/R 1.33

After I got this one I found another Garrett GT for sale. I don't know much about it yet, but I think it is a better choice if I can make it fit.

Compressor:
Inducer 76 mm

Turbine:
Exducer 88 mm


When I step on it the converter is loose enough to let the engine rev to 3000+ rpm instantly and the turbo starts building boost.

You get an idea here: http://www.joby.se/video/joby/2007-08-09.mpg

 

It can be done. Another crazy build up with stock internals.
http://www.theturboforums.com/smf/in...?topic=61219.0

 

can you post cam specs (just curious)...

 

Already posted above. It is not a big cam.

CompCams 12-404-04 cam (LSA 114, duration 222/226 @0.050, lift 0.464/0.464 )

 

You edited the cam duration in the original post. That GT45 has an oddly small compressor. I have a GT4294 off a diesel that has the exact specs as the unit listed at turbobygarrett.com. 69mm inducer, 82mm exhaust wheel, T6 1.28 A/R turbine. I plan to install it on a stock TPI 350ci with a 218* I/E, 110LSA cam. Something like that would probably work well for your setup. It is a better fit to your engine than what I am putting it on. The bore-less comp. wheel on it is less than optimal. I do hear that the shafts break under high loads.

That GT45 you have seems like the exhaust wheel and turbine would fit your application decent.

 

I found a typo in the cam duration. I had written 222/225 instead of 222/226 as it should be.

So your GT4294 has the following spec.

Compressor:
Inducer 69 mm
Exducer 94 mm
A/R 0.60

Turbine:
Inducer 82 mm
Exducer 75 mm
A/R 1.28

 

surely this isnt safe lol

 

awesome #'s JoBY

 

I am running -4* @ .050" on the turbo car too. I like the cam and do not plan on changing it. The specs are 216* @ .050" I/E, 110 LSA. 355ci engine.

I couldn't find the measurements for the GT42 I have so I pulled the comp. housing and turbine and did the measurements again so I don't give bad info.

As measured with dial calipers GT4294 turbo:
Exh In: 82mm
Exh Out: 75mm

Comp In: 70mm
Comp Out: 94mm

Turbine inlet hole: 42mm x 61mm (2 hole split housing)
Turbine A/R: 1.28 diesel flange
Comp. A/R: 0.60

The turbine is a diesel flange. Notice how much bigger the inlet hole is compared to the T4 flange. You can get the specs for the flange for the T4 at turbobygarrett.com.

EDIT: One other thing. The comp. wheel is bore-less. That is, the comp. nut is built into the wheel. The shaft is known to be weaker because of this. It is a stock Detroit S60 series turbo if that helps in your search.

 

whats not safe about it. That motor has more dyno and track time thet a TON of big $ built motors. Its survived numerous floogings. As long as the tune is on par I don't see anything unsafe about it.

You gotta know when to say when and he did. He wasnt spinning it to the moon for a rod to let go and have a catastrophic failure. So at most he would have popped the top ring land off a few pistons if anything.

/hijack off.... back to the vette...

 

dont mean to get off topic but stock cast internals are not rated to handle that power..not by a long shot...thats not safe

but wow that is impressive... those turbos may seem small but i think thats perfect..why go bigger? I wouldnt run anymore boost/power thru that combo

 

I played around with the calcs for the 1.28 A/R diesel flange comparing it to the GT42 T4 flange turbine maps. The 1.28 A/R diesel flange equates to a 1.89 A/R T4 flange. Using the the GT42 turbine maps it would choke around 50 lb/min. Comparing that to the GT47 exhaust wheel and turbine A/Rs it would flow more than the .96 A/R housing. I am not sure what to make of the results, but 50 lb/min is a lot of flow for a turbine. The GT47 is a much larger wheel and an open inlet diesel flange so that really changes things a lot.

I won't really know how the 1.28 A/R diesel housing works until next Summer. Someone was running a similiar turbo (if not exact) at turbomustangs.com and said it spooled around 3500 RPM on a 350ci close to or stock.

 

how many miles on this set up with stock short block?

 

I don't know exactly.

I took the Corvette on three longer trips this summer.
Those three trips add up to about 500 miles.
I have driven a lot more than that locally.

 

Looks OK, not sure I would like to be the guy changing spark plugs!

Please elaborate on the pully system used?

How hot does the car get after driving it for an hour or so, or on the track?

I was going to do a T4 rear mounted turbo mounted between rear batwing cover and gas tank utilizing duel 3" into 1 wastegate and then running 3" oval tubing under floor boards along C-Beam up to front coming up in front of radiator to TPIS intake. On e85 gas it shouldn't need an intercooler and will allow engine cooling with less restrictions in front of it!
My winter project!