305/45/r17 mickey thompson et street R

 

thanks man, cam is btr stage 3 218/224 .553/.553 110+0, trans is 4l65e, I bought the truck as an Na truck that a guy was building and just seemed to have gave up or lost interest, he built the tranny so im not to sure on what parts are in it but its never slip or missed a beat so far, ive thought of replacing it but so far it hasmt given me a reason too, converter pct3800, rear gear Detroit locker with 342's, tire 305-45r17 and front I'd have to look but naturally smaller then that, shift point 6400, intake is a knock off brand sheet metal intake eith a 102mm throttle body.

 

A quick search says those trucks wiegh about 4200 without driver , so right about the same as mine . The thing that stands out to me is the intake, probably killing mid range power . It's also the cheapest thing to change , can get a tbss/nnbs intake from a wreckers dirt cheap and no need for a larger throttle body at these power levels . The fact that you say it's not spinning may be the result of lost torque around the stall speed - it may also be part of the reason the trans is still alive LOL. Can you log at the track ? Would be good to know how fast boost is coming on. Our trucks are quite different but I've got mine to 60' just under 1.7 - traction limited, leaving on vacuum. You can easily get into 10s without running 1.5s in the 60' if you have enough power up top

 

you think the trail blazer intake would actually make a difference, and it definitely spins ive just been heating the hell out the tires in the burn out box. I spin the tires through 3rd gear, the track I go to does a really good job of preping the track so mostly everyone there is hooking up. I also set my gate pressure at 5 psi, im not sure if that makes a difference or not, possible I need to adjust that a bit? Maybe if I bump that up a bit and bump my 2 step a bit I could get there, regardless I ordered the new turbo and the 4 inch piping. My tuner seems to think the turbo I have is the issue because of the exhaust housing being to small on top of the 3inch piping. What made me believe him is when I had the exhaust hooked up it went 11.7 and when I opened the cutoff it went 11.5.

 

The turbo is probably going to help but I run that early cast 7875 with .96 housing on a 6L and go 10.7s at 126.75 at a 4420 lb RW truck with bad aero, rel3rd went well in the 9s with it at similar wieght but much better aero ( firebird) so there is more potential with the current turbo - just saying. Obviously lots of variables in different combos but would like to see you in the 10s without breaking the bank

 

Also as far as logging goes I haven't purchased hp tuners because my next move after the new turbo will be either putting a holley or hp tuner core ecu on the truck so I couldn't convince myself to pay for hp tuners when I have that plan in the future

 

Glad you made it out to the track! 11.5 is no slouch. But, I understand the need for a 10 second slip. As others have said, with some tweaks here and there, you can do it with your current combo.

Good luck!

 

thanks man and my goal before I started the turbo process was to have a truck that I could drive to the track with all my basic functions still usually, heat, ac, radio, power steering, etc, and me driving it to the track not trailering it and running a 10 second pass and then driving it home. Daily driver 10 second truck. I'm getting close but not quite there.

 

Congrats on the 11.5, nice baseline.

Maybe you could list out what your current combo is, it has been a while.

But basically if you weren't spinning and it just drove out you need to leave on more power.

I think I read 6400 shift points?

 

What is the current turbo ? I was thinking it was a 7875 with .96 housing but I was looking through this and didn't find what's on it listed anywhere or did I miss it ?

 

*sbe gen 3 5.3
*243 heads port polished and milled .040
​​​​​*btr stage 3 truck cam, specs listed a few post above with dual 660 springs and trunnion upgrade
*102 mm knock off sheet metal intake and throttle body
* 4l65e unknown mods to tranny as the guy i bought the truck from did the work on the tranny, it has a fairly decent sized cooler
* fuel injection clinic 80 lb injectors
* dual aeromotive 340 pumps with 6a lines and flex fuel sensor( truck is currently on e85)
*342 gears with detroit locker
* suspension brand I'm not sure as in came on the truck but I know there yellow(doesn't look factory) i guess i could look for a part number
*2/4 drop, frame is c-knotched, truck also came with this done
*cx racing 76mm turbo kit, well that was the start, as you guys know I've done some major modifications on this kit to make it work
*lnc-2000 i kept from the nitrous setup but im only using now for the 2 step
*turbosmart e street 40psi boost controller
I may be missing something but I think that's the majority of it, and yes correct my shift point is 6400. Should i raise it?

 

the current turbo is a 76mm .81ar cx racing turbo but the new one i have coming in the mail is the 78/75 that I listed a few post back

 

That is a small exhaust side .81 on a 65mm turbine, I'm sure you will see nice gains with the new one

 

This is the specs for the one that is on the truck and that's exactly what my tuner and a few guys I know with turbo trucks are telling me. They said I actually had a good time considering what I had to deal with. The new turbo I ordered is 1.25 AR


2.5" Compressed Air Outlet
- Wet Floating Bearings
- Oil Cooled
- 1/8" NPT Feeding. M8 x1.25 Return Flange Mounting Screws
- Standard T4 Flange
- 500-800 HP
- 76mm Wheel Compressor
- P Trim .81 A/R Turbine
- 102.4mm/76.7 Compressor Wheel
- 74.1mm/64.6mm
- 3" V-band Hot Side

 

Thanks for sharing the details.

Are you going to dyno with the new turbo? If so it will be interesting to find out where it makes peak HP, that will influence your shift points. Your shift points will be best figured out at the track though you can figure out a starting point. Let's say you are runnning a 3200 converter and you make peak HP at 6300. You might figure out that the truck is quickest with shifting a good amount past peak HP, because of the RPM drop on the shift. Does that make sense?

Also you need to leave on more boost to 60 in the 1.5s.

 

my tuner I go through has his shop on his property behind his house and he actually just got a dyno about a week ago and he was doing all the concrete work last time I went there so we should be able to get it on the dyno when we put the new turbo on and my converter is a pct3800, I forget to mention that. We will probably keep it around 16.8 pounds. I actually had looked into the gate pressure thing through turbosmart and they said my gate pressure should be half of my peak boost and I only had it set at 5 pounds so I'm assuming i was slightly low on gate pressure. Also yes it Definitely makes sense. I'll talk to my tuner when we install the new turbo and see if we raise the rpm a bit and see if it helps. Should I be concerned with setting the boost by gear or is that really only for if I'm having fractions issues?

 

Are you stock ECU? And/or how are you controlling boost?

So for sake of discussion, let's say you were leaving on 5 psi (are you using a 2 step?), and you had all the boost come in by 1.25 seconds. That was your baseline. The 60 is mostly based on how much power you leave on so to 60 better you have to leave on more boost.

Let's say you dial in the new turbo, and your baseline pass is 5 psi and you cut a 1.75. It's not going to run 10's at that power level quite yet. Next pass you come back around and leave on 6, and see what happens with the 60. I'd try to get the 60 in the 1.6s to start though I don't have personal experience dialing in a 4000 raceweight vehicle.

Now, shift points. If the turbo makes peak at 6200 but carries out good power to 6800 hmmm. You want the engine to stay in the best part of your power band during the whole run. So let's say at 6200 you make 650rwhp and by 6800 it's dropped 50rwhp. It's a bit of trial and error to figure out shift points. But put it this way, if you shift at 6400 and your RPMs drop to say 4800, you should look at the sheet to see how much power you are making there. 600rwhp at 6600 is better than 450rwhp at 4800, does that make sense? I'll say this as a generalization if you make peak HP say at 6200 and you have a 3800 converter you'll be watching the shift drop (1500 RPMs is a lot, 1000-1200 would be better just to note, and race cars drop even less).

Also, and I touched on it a little, you have the boost ramp, ie. how quickly you make all your boost. So class cars are "all in" that is to say make all their boost anywhere under 1.25 seconds. You will find combos who are all in by .9 seconds.

 

yes I'm using a stock ecu and i have a turbosmart electronic boost controller, and yes I also have a 2 step. It has a boost by gear feature but I haven't used it. I just set the duty cycle and the wastegate spring up to where it gets my 16.8 pounds and I set the gate pressure to 5 psi, so basically I'm leaving on 5 pounds and it builds to 16.8 pounds at its own rate which is fairly quickly but I'd imagine if i left on lets say 8 pounds it would probably do much better And yes the rpm definitely makes sense, sounds like I definitely need to raise my rpm and my gate pressure then. I didnt realize the things your explaining.

 

And you are not using C02 right?

So let's say your raceweight was 4000 or more. I'm thinking a good slip might look something like 10.9@127, 60 is 1.50-1.60 in there, let's say 1.55 for conversation sake. You'll need to run 100-103 mph in the 1/8th and somewhere between 6.9-7.1. I went back and looked at your slip, 7.50 in the 1/8th. That's promising.

So your baseline is 1.9 11.5@121 and I recall seeing 96 in the 1/8th.

Leaving on more power (boost) will improve the 60 and the over all pass, I would dial that in first. Car is in peak boost quicker since you are leaving on more. Then you need to watch RPM drop on the shift and try different shift points. I assume you are not running a fancy triple disc converter and not locking the converter during your pass?

Another thing to watch is any sort of boost drop after the shift.

If your boost ramp was say 1.7, there is a lot left. I'd shoot for 1.25 all in.

Were it mine, I'd work the 60, and then work the shift points after because the truck will pick up a lot leaving on 6-8 vs 5. So after that I'd mess with shift points. Let's say they are 6400 now. I'd try 6600 across the board, then 6800. If it picks up both times I'll try 7000.

 

makes alot of sense, and no I'm not using co2 and my rpm does drop a bit when I shift gears and one thing I did mention in a previous post it that I think the smaller housing was hurting me too because 1st and 2nd were struggling a bit, they would only get to about 13 psi and 3rd gear is when id see the 16.8 psi and i tried turning the boost up a bit but it only seemed to go up on the big end(3rd gear) so hopefully this new turbo with the bigger housing and 4 inch exhaust will stop that from happening and ill definitely turn the gate pressure up to about 8 psi and like you said bump my rpm up a bit. Ill definitely do that on the dyno with my tuner and see if I get some power gains by doing that. Turbo comes in tomorrow and all the piping should be here by this weekend so shouldn't be long until I make the changes.