Downgrade from twins to single 472?

[JoshH]

So as some of you probably know, I'm a big fan of compound twin turbo setups. I've had several different kits, and I have always really liked them. The shop truck currently has an S480/S364.5 with fairly tight turbine sides on both turbos. It is a blast to drive on the street and makes good power.

You may also remember that a couple of months ago I broke the crank in the stock motor in the truck and decided to pull the built motor out of the dumpster. The motor is exactly as it was in the dumpster except I removed my 12mm CP3 for dual stock pumps, and I removed the single S472 to install my twins. The motor out down 970 on a chassis dyno (I know, dyno numbers) on a 2500 uS tune with 100% injectors, but I was never able to work out all the bugs on the new setup before I pulled the motor out to verify that power.

So fast forward to Saturday. I took the truck to the track and made one pass on a 2600 uS tune (same injectors I used in the dumpster) and trapped 125 mph. According to CompD calculator (which has always seemed pretty accurate to me), that's about 800 hp to the ground. With a stock motor and 40% injectors (same pulse width that actually peaked full fuel higher in the rpm band), I was able to trap almost 120 mph which equates to 700 hp. I was really expecting to be in the 130+ range and in the 10s, but I was a little disappointed.

So here's what is on my mind, I'm thinking maybe the tighter turbine housings and smaller turbine wheel in the valley turbo is causing flow problems and killing power. I'm seriously thinking about removing my twins and bolting on the 472 in their place. Does this sound crazy to anyone else? I will probably do it either way because I've never run a larger fixed geometry turbo, and I would like to see what it is all about. That said, I would love to hear opinions from others on whether or not you think I'm expecting too much out of the truck or if you agree that maybe my setup is killing top end power.

 

[Chevy1925]

What rpm you turning? When coker had those on his old truck, I thought the 1.1 housing on the big charger was too tight but a drive pressure gauge would tell you more. You got one in that bad boy? I know Blake Crenshaw has track proven 950hp on 100 overs, modded lly charger and box stock 480. Now I don't know what he trapped but Goldie was a cc/sb running low 11s

 

[zakkb787]

I'm no expert in this at all, but I would imagine the smaller 364.5 may be choking you. Instead of putting a whole new kit, why not just change out the turbos? Maybe a s485/s369sxe and see what that nets you. Personally, after I get things paid I'm going to try out a s475. Probably billet or may even go batmo. That's all big dreams tho. I hear big singles are fun

 

[JoshH]

What rpm you turning? When coker had those on his old truck, I thought the 1.1 housing on the big charger was too tight but a drive pressure gauge would tell you more. You got one in that bad boy? I know Blake Crenshaw has track proven 950hp on 100 overs, modded lly charger and box stock 480. Now I don't know what he trapped but Goldie was a cc/sb running low 11s

I do not have any gauges on the truck, but when Russ had it, he said drive pressure stayed close to 1:1 until you got past 3500 rpm. I have it shifting around 3800-3900 rpm. I also dropped the valley turbo down from a .90 A/R to a .83 A/R.

As far as changing turbos goes, I'm not going to buy turbos. I have the 472 sitting on the shelf, and it will bolt right on my pedestal. I'll have to build some piping to make it work, but that should be pretty simple.

 

[Chevy1925]

Oh damn, yeah you tighten that valley turbo way up! You are probably correct in that you are choking it up with all that fuel. Didn't try a smaller tune did ya?

 

[zakkb787]

I do not have any gauges on the truck, but when Russ had it, he said drive pressure stayed close to 1:1 until you got past 3500 rpm. I have it shifting around 3800-3900 rpm. I also dropped the valley turbo down from a .90 A/R to a .83 A/R.

As far as changing turbos goes, I'm not going to buy turbos. I have the 472 sitting on the shelf, and it will bolt right on my pedestal. I'll have to build some piping to make it work, but that should be pretty simple.

Ah gotcha. I'd imagine even if it didn't make anymore power it'd still be a whole other animal. I'm In For results:thumb:

 

[JoshH]

Oh damn, yeah you tighten that valley turbo way up! You are probably correct in that you are choking it up with all that fuel. Didn't try a smaller tune did ya?

I did drop it down to a 2300 uS tune for eliminations, but I was on the brakes at the end of my first pass and trapped about 106. The second pass was spin city, and I had to peddle it several times out past the 330' mark. I honestly didn't even pay attention to the trap speed because I was so frustrated about how bad it spun. Stupid G80!

 

[Chevy1925]

lol I saw the video. Pretty sure it was giving you the finger in the burnout box too. Not gunna lie, the recovery after peddling and how quickly everything came back on full power was something you don't see much on the race track, specially cause it grabbed and went!. Usually it's black smoke till the 1/8 before anyone gets power back lol

 

[JoshH]

Those twins may be limiting my power, but they spool amazingly quick!

 

[SickLL7Crenshaw]

Goldie runs 11.10s@124mph in Albuquerque. We weighed it with Dylan in the drivers seat and it's right at 6800lbs. James is correct on the turbo and fuel setup. Pulse was a 2250uS in Albuquerque. Runs the same times in Hobbs on a 1950uS. (1800ft lower in Hobbs) Shift points are at 3600. Anything past that we run slower, gain higher drive and egts. (Truck is out of air especially in Albuquerque).

Truck ran pretty dang good Saturday Josh! I think it would still be more fun on the street if you went back to a .90 in the valley and even a 1.32 on the 480. Thats just my idea which I think you'd for sure get in the 130s and I believe you could get it to light fast without any issues. But then again big singles with some spray are a blast on the street.

It was good to meet you Josh, enjoyed the talk we had. Your little pickup was one of my favorites there :thumb:

 

[Ne-max]

A gate would help a lot if you want to keep it the way it is. Valley charger is killing ya.

 

[S Phinney]

One of the trucks I tune we had 100 overs a 366/480 kit and it would trap 125 on 1600 us. The chargers had a internally gated stainless on the high pressure and a v band 1.30 stainless turbine on the atmosphere. It was at 7400 lbs area with driver. I would stay with the compounds and change turbines myself. My 200 over twin kit almost like the lly I was talking about Tuning will be a very strong truck. I recently got it running and have beeen out of town working so I haven’t had much time to finish up on it but I do expect to trap 130 or better with it.


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[JoshH]

I agree with you all about the turbines, and I will probably do something about it if/when I put them back on. Like I said though, I already have this 472, and my motor has a 9100 SoCal cam in it that should breathe really well at higher RPM. I really want to try something different (for me) and run this single on the street. Thanks for confirming my suspicions though.

Blake, it was nice meeting you, and I also enjoyed getting to talk.

 

[SSchmi5519]

What are the turbine specs on your S471?

 

[JoshH]

The 472 has an 87mm turbine in a 1.00 A/R T4 housing.

 

[Chevy1925]

I agree with you all about the turbines, and I will probably do something about it if/when I put them back on. Like I said though, I already have this 472, and my motor has a 9100 SoCal cam in it that should breathe really well at higher RPM. I really want to try something different (for me) and run this single on the street. Thanks for confirming my suspicions though.

Blake, it was nice meeting you, and I also enjoyed getting to talk.

ah so the cam aint helping things either.

the 472 sounds like a better suited setup for what you are after

 

[brokesmoke]

I'm running a S475 single on basically stock fuel and love it. No way I'd run compounds personally with how I drive.

 

[bigmackmiller]

Will there be any other hurdles with switching the setup? Converter etc...

 

[JoshH]

Will there be any other hurdles with switching the setup? Converter etc...

Converter is way loose 3,000 rpm precision. I will need to build some plumbing for intake, exhaust, and intercooler tubes, but none of that should be much of a problem.

 

[bigmackmiller]

I say go for it, think it would be fun to switch it up for awhile, no doubt you can handle the fab :thumb: