Problem making hp

[zexystang2]

Ok so I have a 4.75 forged short block with cnced port and polished heads with stock cams with 20 degree phase limiters and stock valves etc. The power adder is a turbo thats .68 a/r hot and .70 a/r cold. The boost was set at 15 p.s.i and only made 421 hp and 500 torque at 4200 rpm then falls off. The tuner was stumped he tryed everything he could think of during 15 different pulls and it didnt get better. The only thing he saw wrong was that he set both cams to retard between 9-14 and one cam did that and the other was all over the place. Could this be do to a bad cam position sensor or the vct oil control solenoid? And does anyone know if this could hurt the hp that bad.

 

[JeremyH]

More specs on the turbo/kit? Whats the compression/what plugs you runing?
Who is tuning it?
What was the a/f/timing?

Why the cnc heads with stock cams and limiters?

Does sound like a bad phaser or solenoid but if the tune orders it to retard and it doesnt match you will get a cel and a code.

 

[niner555]

Ok so I have a 4.75 forged short block with cnced port and polished heads with stock cams with 20 degree phase limiters and stock valves etc. The power adder is a turbo thats .68 a/r hot and .70 a/r cold. The boost was set at 15 p.s.i and only made 421 hp and 500 torque at 4200 rpm then falls off. The tuner was stumped he tryed everything he could think of during 15 different pulls and it didnt get better. The only thing he saw wrong was that he set both cams to retard between 9-14 and one cam did that and the other was all over the place. Could this be do to a bad cam position sensor or the vct oil control solenoid? And does anyone know if this could hurt the hp that bad.

When using limiters, make sure your tuner has no greater value than 20 deg. placed in any of the cam phaser timing tables. Even though he is commanding 9-14 deg of cam retard, if a value of 20 deg. or higher is placed in ANY cell, the computer gets very pissed-off. Look up the instructions for COMP's limiter kit, it has pics of all the SCT VCT software tables and how to set them.

Aside from that, if you are using the stock cams, you probably do not need to retard any more that 9-10 deg. above 6000 rpm.....14 deg. seems excessive. I would have 0 deg. up till 4500 rpm and gradually feed in the retard as rpm goes up.

All that being said was assuing the cams were installed correctly. Do a quick cranking compression test and see if one side of the engine is higher/lower than the other side. If they differ, the cams were installed incorrectly.

Good luck!

 

[zexystang2]

More specs on the turbo/kit? Whats the compression/what plugs you runing?
Who is tuning it?
What was the a/f/timing?

Why the cnc heads with stock cams and limiters?

Does sound like a bad phaser or solenoid but if the tune orders it to retard and it doesnt match you will get a cel and a code.

It is the on3 turbo kit with the on3 supplied turbo.The compression is 9 to 1 and I did a compression check and all were at 150. I'm running the step colder hto's gapped 30. The a/f is running around 11.5's under boost. And I had 127650's in at first but when I got tuned it only got 400 hp so I thought it was to much lift and cam overlap for a turbo, so I changed back to stock. And I really dont wanna mention the tuners name just incase this is a sensor or something wrong on my end.

 

[niner555]

the compression is 9 to 1 and I did a compression check and all were at 150. I'm running the step colder hto's gapped 30. The a/f is running around 11.5's under boost. And I had 127650's in at first but when I got tuned it only got 400 hp so I thought it was to much lift and cam overlap for a turbo, so I changed back to stock.

Based on what you are saying, I am guessing it's something in the tune or a VCT signal/sensor/solenoid issue on that side of the engine that is having problems controlling the cam. I have seen 20 degree retarded cams kill 40+ hp on an N/A 3V engine, so I can see where it could kill 100+ on a turbo application.

Until you can get the cam on that side of the engine controlled properly, I wouldn't mess with anything else.

BTW, once you get everything sorted out, I would seriously consider putting those 127650 cams back in. They will make major power above 6500 rpm.....maybe not the best cams for a street turbo set-up, but will really run good at the track.

 

[zexystang2]

Just wondering If I put 10 degree lockouts in would this alleviate all of this and work fine with a turbo?

 

[niner555]

Just wondering If I put 10 degree lockouts in would this alleviate all of this and work fine with a turbo?

Sure...it's kind of a cave man way of doing it, but it will def. keep the cams locked in place. Won't really affect peak power output, but the downside to locking the cams is that cam retard really hurts power below 4500 rpm. On an N/A engine, you will typically lose up to 20 ft/lb tq if you retard the cams that much at lower rpm points. That tq loss will affect your spool-up. If this is primarily a street car, I would try to figure out why the cam is not controlling properly and fix it right......no sense in throwing away free hp by locking them IMHO. But, if this is mainly a track car and 4500 rpm plus power production is your main focus, you really won't lose much by having the cams locked.

 

[JeremyH]

I have comp limters and my max retard up top is 9 degrees as well. Dont really make any more power past that on a turbo setup.

Lockouts would be the easiest way sure, but like mentioned you will loose tq down low and hp up top.

Check out Earl's setup he has a twin turbo setup with stock cams locked out at 15psi that will give you a rough idea of the power you should be making.


http://www.s197forum.com/forum/showthread.php?t=71525&highlight=dyno



How many degrees of timing?

 

[klaw]

I have Comp 127550's on my Whipple setup with Livernois limiters - making 630 RWHP at 14psi. Both the 550's and 650's are SPR (spring & phaser mods required) cams so you've probably upgraded your springs. I've seen issues with phasers trying to modulate against the heavy springs and aggressive cam ramps. I would reconfirm physical cam timing and, assuming that checks out I'd swap out the phasers to the latest revision.

 

[zexystang2]

Update. So I swapped out the passenger side vct solenoid and went and data logged it on the street. Both cams were staying close between 9 and 14 now. I have to wait till Monday to dyno it again but hopefully this works.

 

[BruceH]

Update. So I swapped out the passenger side vct solenoid and went and data logged it on the street. Both cams were staying close between 9 and 14 now. I have to wait till Monday to dyno it again but hopefully this works.

Glad to see you got it. FWIW I've got the most hp with my cams by retarding at wot. Currently have 18 degrees commanded at high loads beyond 3k iirc. Not exactly a direct comparison with yours but it's worth it to experiment some. I may even try some more as my 20 degree limiters are actually allowing 22 degrees momentarily at times according to my datalogs.

 

[niner555]

Update. So I swapped out the passenger side vct solenoid and went and data logged it on the street. Both cams were staying close between 9 and 14 now. I have to wait till Monday to dyno it again but hopefully this works.

Awesome, glad to see you made some progress. Let us know what it makes on the dyno!

 

[zexystang2]

Bad news. I went back out today to data log it again just to make sure before I carried it to the dyno tomorrow and the same cam was all over the place again. So i'm back at square one.

 

[toorbeenee]

those cams are no good with turbo,i had them before

 

[JeremyH]

He has stock cams, he already got rid of the 650s


Try swapping the cam position sensors from left to right to rule out the sensors.

 

[toorbeenee]

BTW, once you get everything sorted out, I would seriously consider putting those 127650 cams back in. They will make major power above 6500 rpm.....maybe not the best cams for a street turbo set-up, but will really run good at the track.

i was talking about this

 

[JeremyH]

i was talking about this

 

[toorbeenee]

sure buddy

 

[zexystang2]

Still having problems so I got a precision 6766 cea .81 a/r to try to rule out not having enough cfm from the on3 turbo and i still only dynoed 481 rwhp at 22 pounds of boost. Cam angle 0 was still all over the place. DOES ANYONE KNOW IF ONE CAM WITH ERRATIC TIMING CAN MAKE ME LOOSE OVER 150 HP?

 

[RiskyBiznes05GT]

Still having problems so I got a precision 6766 cea .81 a/r to try to rule out not having enough cfm from the on3 turbo and i still only dynoed 481 rwhp at 22 pounds of boost. Cam angle 0 was still all over the place. DOES ANYONE KNOW IF ONE CAM WITH ERRATIC TIMING CAN MAKE ME LOOSE OVER 150 HP?

If I was in your shoes I would drop the car off at a capable tuner/shop that can address this. Throwing parts at it is not the best solution.