What would cause this?
10-27-2009, 09:06 PM
#1
TECH Fanatic
Thread Starter
iTrader: (12)
Join Date: Jul 2004
Location: Roanoke Va
Posts: 1,234
Likes: 0
Received 0 Likes
on
0 Posts
What would cause this? Every time I have had my truck on the dyno it has a weird drop right at peak boost. It only does it above 9psi so I guess it could be a few things but I wanted some opinions. Here is my setup and dyno graph.
stock 6.0L
STS kit, FMIC, Meth, TC 76 BB turbo w/.96 housing
z06 cam and valve springs
built 60e by performabuilt and Yank trt3000 stall
This dyno run was at about 13psi and 20 degrees of timing with no knock and the converter unlocked. The truck pulls good on the street and it has ran a best 11.81 on 11psi. Could it be blowing through the converter or trans slipping on the dyno? Any ideas are welcome. Thanks
stock 6.0L
STS kit, FMIC, Meth, TC 76 BB turbo w/.96 housing
z06 cam and valve springs
built 60e by performabuilt and Yank trt3000 stall
This dyno run was at about 13psi and 20 degrees of timing with no knock and the converter unlocked. The truck pulls good on the street and it has ran a best 11.81 on 11psi. Could it be blowing through the converter or trans slipping on the dyno? Any ideas are welcome. Thanks
Last edited by 2ktransam; 10-27-2009 at 09:16 PM.
11-01-2009, 10:29 PM
#6
TECH Fanatic
Thread Starter
iTrader: (12)
Join Date: Jul 2004
Location: Roanoke Va
Posts: 1,234
Likes: 0
Received 0 Likes
on
0 Posts
I had it back on the dyno today and it did the same thing again with the tighter plug gap so that wasn't it. It actually falls off right when it reaches full boost and the wastegate opens all the way. Could it be something with the wastegate or deffinitely valve float? It made 540rwhp today at 14psi but at 4800 rpms.
Trending Topics
11-08-2009, 10:56 PM
#10
TECH Fanatic
Thread Starter
iTrader: (12)
Join Date: Jul 2004
Location: Roanoke Va
Posts: 1,234
Likes: 0
Received 0 Likes
on
0 Posts
pressure tested all piping
pulled air filter
with and without meth
closed gap on my spark plugs to .27
locked the converter for one run to check for slipage
changed my wastegate to vent to atmosphere
Nothing seems to change on the dyno so I'm going to upgrade my springs and change to the 7.425 push rods. My problem gets worse the more I up the boost. At 8-9psi my power peaks and stays flat to 5500 but at 14psi I lose 50rwhp from 5k to 5500.
11-08-2009, 11:13 PM
#11
Restricted User
iTrader: (36)
Join Date: Sep 2008
Location: Alliance Nebraska
Posts: 1,268
Likes: 0
Received 0 Likes
on
0 Posts
ya it sucks... I think im gonna break down and try new springs when i get the money for them.
What springs are you running? I am running PRC dauls with only 8000 miles on them.
Im really starting to wonder if its the ls6 cam... I posted a link in my thread to a thread in with a bunch of other dyno sheets where ls6 cams were used on several differnent motor setups and they all did the same!
kinda makes me wonder??????
What springs are you running? I am running PRC dauls with only 8000 miles on them.
Im really starting to wonder if its the ls6 cam... I posted a link in my thread to a thread in with a bunch of other dyno sheets where ls6 cams were used on several differnent motor setups and they all did the same!
kinda makes me wonder??????
11-09-2009, 07:54 AM
#12
TECH Fanatic
Thread Starter
iTrader: (12)
Join Date: Jul 2004
Location: Roanoke Va
Posts: 1,234
Likes: 0
Received 0 Likes
on
0 Posts
ya it sucks... I think im gonna break down and try new springs when i get the money for them.
What springs are you running? I am running PRC dauls with only 8000 miles on them.
Im really starting to wonder if its the ls6 cam... I posted a link in my thread to a thread in with a bunch of other dyno sheets where ls6 cams were used on several differnent motor setups and they all did the same!
kinda makes me wonder??????
What springs are you running? I am running PRC dauls with only 8000 miles on them.
Im really starting to wonder if its the ls6 cam... I posted a link in my thread to a thread in with a bunch of other dyno sheets where ls6 cams were used on several differnent motor setups and they all did the same!
kinda makes me wonder??????
I read through that post and I don't understand why some people like Parish and WJMark have had great luck with the ls6 cam and a turbo but some people have trouble.
11-16-2009, 09:22 PM
#13
TECH Fanatic
Thread Starter
iTrader: (12)
Join Date: Jul 2004
Location: Roanoke Va
Posts: 1,234
Likes: 0
Received 0 Likes
on
0 Posts
I installed PRC duals tonight and they didn't seem to help any. I did a few pulls and my fuel trims didn't change any and it still feels like it struggles above 5k. Any other ideas? could it be a back pressure problem since it is a STS kit?
11-16-2009, 09:29 PM
#14
TECH Senior Member
iTrader: (23)
Join Date: Jul 2004
Location: Houston, TX
Posts: 9,853
Likes: 0
Received 0 Likes
on
0 Posts
This is a graph from a TC76 BB .68 AR on a 6.0. It's from the member Stock48. It peaks at like 4500. What size engine do you have? I think the turbo is choked up out top.
11-16-2009, 10:05 PM
#16
TECH Fanatic
Thread Starter
iTrader: (12)
Join Date: Jul 2004
Location: Roanoke Va
Posts: 1,234
Likes: 0
Received 0 Likes
on
0 Posts
I have a stock 6.0L with the z06 cam. I do have the .96 exhaust housing on my turbo and I think that dyno was with a smaller AR but you might be right. I wish I understood compressor maps so I could figure out if I am pushing to much air flow for this turbo.
11-16-2009, 10:16 PM
#17
Restricted User
iTrader: (36)
Join Date: Sep 2008
Location: Alliance Nebraska
Posts: 1,268
Likes: 0
Received 0 Likes
on
0 Posts
So you changed valve springs and it didn't help, now maybee i wont change valvesprings. This **** is driving me crazy!
11-16-2009, 10:21 PM
#18
TECH Fanatic
Thread Starter
iTrader: (12)
Join Date: Jul 2004
Location: Roanoke Va
Posts: 1,234
Likes: 0
Received 0 Likes
on
0 Posts
That's cool man. I think we might be chasing the same problem. I hope you figure it out so I can stop spending money. This is driving me crazy.
11-16-2009, 10:41 PM
#19
Restricted User
iTrader: (36)
Join Date: Sep 2008
Location: Alliance Nebraska
Posts: 1,268
Likes: 0
Received 0 Likes
on
0 Posts
lol, i figure mine out youll be the first person to know!!!
11-16-2009, 11:26 PM
#20
TECH Senior Member
iTrader: (23)
Join Date: Jul 2004
Location: Houston, TX
Posts: 9,853
Likes: 0
Received 0 Likes
on
0 Posts
You may want to look into the TC78 BB 1.15 AR. That should give you more up top. That's the turbo I've got my eye on for my 6.0. I don't want to fall into the same trap you guys did. I want super quick spool and great pull up to 6k rpm.