My work bought a trailer dyno and we were training on it today so I got to stick my truck on it for a few runs. It made 525 RWHP 5300 RPM and 615 RWTQ at 4200 RPM at 8 psi. I didn't have much time on it so I upped the boost to 12 psi and made one run before I had to take it off. It made 581 RWHP at 5000 RPM and 694 RWTQ. It was pretty rich at 10.5:1 AFR. I had noi time to tune but I thought it did alright being such a mild combo. Pump gas 91 octane. I think my springs may be a little weak or the small turbine stock manifolds are causing backpressure issues. I doubt I will do much as it is a pretty hairy street combo. The 581 pull makes it close to 700 at the crank and it idles with 14" vac and starts every time without so much as a hiccup. So I am pleased Might measure turbo drive pressure for curiosity.

 

Curtis, I wish people who are planning 596,000 cubic inch combos would read this thread. Nice goin man!!!!

 

Very nice! How rough was setting up the Megasquirt? I am a fan of your combo as mine probably won't be a whole lot different, but I'm thinking of using the MS3+Extra for sequential EFI.

Again, Great numbers man! How much that truck weigh?

 

Thanks. I kinda hope the backpressure isn't too far out to lunch because it is alot cheaper to put another set of springs in. I kinda have a feeling that the exhaust side is getting close to maxed out. On 12 psi boost the truck is crazy on the street. It will almost smoke the tires at 50mph with all that mid range torque. You can only go full throttle at 60+ mph in third gear. That is with about 400lbs of added weight to the back compared to on that is stock.

The truck is around 4200 but I havn't weighed it in a long time. The megasquirt is a learning curve but it is great for datalogging and tuning. One it is nailed down the drivability is second to none.

 

So why is it that you want to move from 400 to 451"?

Some serious power for sure for a 'pedestrian' setup!

 

Thanks. I have setup a quick gauge to measure backpressure JUst need to buy some hose to go from the brake line I tapped into the up pipe going to the turbo. Then I will know if I need more turbine or more spring pressure. Is there a tool to remove dual valve springs? I have thought about making my own....

 

Curtis,

This tool works very well, does Comp 930s ok [135 ish seat, 350 ish open] You might be able to use a double ended stud in the head and stud make it work. My Cadillac engine has only 4 bolts holding the rocker ass'ys down, and it works for me. You can adjust it way up or down on the stud. It cams over and holds the spring down, making it nice to swap keepers and such.

http://www.summitracing.com/parts/SUM-906784/?rtype=10


http://www.jegs.com/i/JEGS/555/80521/10002/-1

Nice numbers, btw.

Dave

 

Nice work. Very nice numbers. I'm working on a MS for the ole slant too.

 

Them are some dang good numbers it just shows you don't need big cubes,I realy like the torque #'s it would have to be fun to drive I can't wait for mine to get done .
What kind of dyno is it and how many jaws dropped when seen the #'s LOL!

 

Thanks I will look into it further.

You will not regret the MS IMHO. When you get it nailed down it is great.

I liked the torque numbers because it is a short stroke 400 engine. The converter may have been flashing and making those big numbers but I will take it. It is a Dynocom dyno and we were just runnning inertia runs. Didn't turn up the eddy brake. I was the operator but the training guy help set it up so I think all was good. Running it like that is like a dynojet and my turbo spooled later than on the street it seemed. I will probably turn the boost down to 8 psi as it makes 525 at that. I was hangin around some stiff competion as I just went after my bosses twin turbo dodge diesel. It pulled 771 and 1400+ RWTQ. Then he turned on the NOS and made 850 hp and 1550 tq. Although his was lifting the head and blowing over a little. Plus he has yet to run mid 11s and this year make it down the track with a head gasket in place. So I still have the fastest truck in the shop. LOL. I think I may have hurt some feelings as the diesel guys always talk HP numbers and the gas guy in the shop killed them on the dyno and the track. HAHA.

 

Just to have 500 at the wheel in a street truck is enough to brag about I would just leave it at 12#s and then put some race fuel and bump it up to 15#s at the track they will never see it coming.

 

Well the results are in. I just got back from a test drive and I have excessive backpressure. It has right around 36 psi back pressure at 12 psi boost. I didn't think that exhaust side would choke this early but I did get the smaller exhaust turbine. I think I will crutch it along with some 323 gears to take advantage of my massive midrange torque. Does anyone think I will hurt anything with that much backpressure?

 

I take back running the 15#s LOL,When does it spool?

 

Not sure about exact RPM but 3000 ish 3500 is near instant spool. Kinda small power band though. The converter flashes to around 4000 when boost comes up and looks like I need to be shifting at 5500. If I swap to 3.23s it may be not that bad but I still need to get this thing off the line. I do like telling people that it makes 581 hp and then pause and then say at the rear tires. LOL As long as this high of backpressure doesn't start killing motor parts I just don't have the money to start swapping turbos.

 

Sounds like you need less converter and less gear and just start enjoying it!

 

My Dakota had 2500 stall with the 3.23's it would pull like crazy when boost come in and we all know the turbo on it was ''to small'' but I never looked at back pressure,my combo worked like I wanded it too.I think you will fine with it your not going to try and 8000 RPM's with it.