A brief intro... I'm one of the owners at an import tuner shop (amsperformance.com) and have recently purchased a CTS-V for a daily driver. I like any fast car no matter if it's import or domestic. This CTS-V is heavily modified and it's here's a link to a post about the previous owner made about the power being low. https://ls1tech.com/forums/showthrea...&highlight=427

Well I put her on our Dynojet dyno today and it made 464whp and around 440tq. A few tweaks with HP tuners and the final numbers where 469whp and tq was the same. Tune was decent, with the A/F around 12.9-13.2:1 and timing 22deg at peak tq up to 26 deg at redline. I played with timing and anything past 25deg didn't make much of a difference. I noticed a few things that concerned me. Anything below 2200rpm at WOT the MAF signal goes nutty and timing drops low, although no timing is being pulled. TQ is also low at this point and It will even slightly misfire through the intake.

I'm very familiar with engine performance and tuning but I'm a little new to the specifics of the LS powerplant. Doing research I thought this combo should put down 525-550whp on my dyno.

Here are some specs that I got from the previous owner

Katech 427
AFR 225 heads with 72cc chambers
Fast 90mm intake manifold
LS2 TB
Kooks 1 7/8" headers
3" header back exhaust (loud!!) no cats
Cam?? not sure the previous owner is trying to get specs,
I think it's a comp 24x/24x duration
Static Comp ratio is 11:1

Almost as if it's missing a cylinder or something is seriously wrong with cam timing. The low rpm WOT misfires (out the intake) worry me. The power curve looks ok so I'm thinking the cam timing is probably ok but you never know. I'll post a dyno sheet tomorrow. Any hints?
Tomorrow I'll see if I can switch injectors off with HP tuners and maybe I'll do dyno runs turning off cylinders to see if one's dead.

BTW HP tuners is bad ***. It blows away the OEM ECU tweaking software/hardware we have for Mitsu EVO's and Subaru STi's. We could tune 4 LS powered cars for every one STi, it's that much quicker and easier. Being NA makes it easier but none the less.

-Martin

 

I question whether the cam timing is right. It is hard to say but the motor seems to have all the right parts for a strong 500+/500+ car (427ci, AFR heads, Kooks headers, FAST intake, decent compression). That leaves the cam as the questionable part...also does it have a 75 or 85mm MAF? Does it have an adjustable timing chain? I really wonder what the valve events are right now and if it is advanced or something? Just my thoughts. It might help if you post a graph.

 

Call KATECH all the motor builds have a buildrs stamp and they can run the history for you. I dont know where the stamp is but they can tell u.

 

yea that would be the place i would start as well. Katech should be able to give you specifics about the build and possibly help troublshoot the problem. Id be very dissapointed if my 427 didnt hit at least 500rwhp. Good luck sir.

 

Where are you located??

 

Here is the dyno chart before and after tuning. The only I changed was timing. It was 24-25deg at low rpm and fell to 23 deg up top for some reason. I put it at 23deg low rpm ramping up to 26 deg up.



I did 8 dyno runs this morning pulling an injector plug off each run to see if one of the cylinders was down, but they all lost the same amount of power. So it's not a dead cylinder or bad inject/coil.

 

Located in West Chicago, IL (near St. Charles)

 

Call Katech up. They'll help you out since they built the motor.

 

Katech supplied the short block and I think Arizona speed & sound built the rest.
Next up is a leakdown test.

 

The torque numbers are especially troublesome for an engine that large....they are way off.

Hit the key basics first...

I would advise you to do a leakdown test on every hole and then a cranking compression check on one or two assuming the leak down looks reasonably consistant. The leakdown test will verify everything is sealing up and you have no bent valves or something silly....the cranking compression test may give us a clue if the cam is installed properly....if its less than 150 pounds that would indicate something with camshaft timing or installed position is way off.

Keep us posted...

Tony

PS...With 11 or so static CR and say a 244/248 cam I would expect cranking numbers in the 180 PSI range (give or take 10 PSI) on a healthy engine with the cam installed properly

 

Yes leakdown test and compression test is next. I'll try to do that by the weekend. I wish it was as easy to do as in my EVO

Thanks for the heads up on the cranking compression #'s. I'm used to seeing 140-150 on our low(er) compression turbocharged 4 cyliders.

 

Hey, have you checked the clutch. a slipping clutch would give you lower Trq.
Also did you tune with the Maf plugged in or not.

 

You know Martin, there is a TON of room for a set of 35Rs under a CTS V, and there is a 3bar map HPT can do

72cc chambers seem awfully big. I dont think static compression is 11:1, almost seems it would be lower.


FWIW, AZ power and Sound is out of business last I heard. What color is this car? Buy it off ebay?

Louis ( on NABR too )

 

He could do 11:1 if the piston has 7cc or smaller dish I think.

 

Hey Louis,

Oh yah I already thought about a pair of turbos. But since I'm trying to make it a daily driver i don't want to be replacing CTS-V drivetrain parts weekly.

It's black and yes I got it off ebay.



The car is bad ***, love it but need to figure out the power thing. Can't have my EVO making more power on pump gas than this car.

Doesn't look like I'm going to get any info out of AZ power and sounds so I'm in the dark on the cams, port work, ect.

BTW I tried to do a compression test last night and as one of my mechanics says, 'It's like trying to fist a girl with a p*ssy full of legos" Damn, I gave up and I'll plan my weekend around it

 

You bought Chef old V?? Very nice car. BTW with LT doing a comp test is so much easier then with stock mainfolds on there, but then again a 4cyl is damn easy to do. (non STI) I also thought that Chef had gotten rid on MAF and was on a SD tune?? are you tuning with MAF or SD?

 

It's still a MAF.

 

It's not THAT bad to do a leakdown on a lsx, but no DSM or EVO thats for sure. I'm sure you'll figure it out though Martin. I'm curious to see whats holding it back. You need to start tinkering with these cars more so I can come back with the vette for some dyno time. I'd like to beat my old talon numbers some day

Ed Charboneau (Iowa NABR guy)

 

Just did a compression test on a cylinder and came up with 190psi. I'll do the rest tomorrow along with a leakdown test. While I'm at it I'll pull the intake manifold and check out how the intake runners were ported.
Tony, how can I tell what type of AFR head it is without pulling it off, chamber cc, runners, I see a serial # on the front of the head, will that help?

 

that will prbably tell them what it was when it left the factory...no way to tell if it had machine work afterward I bet...without pulling it