Need help.... lost hp go to a 90/90 setup
Need help.... lost hp go to a 90/90 setup I had a 78mm Fast intake and ported stock tb on my car and it dyno'd 442/400. I then decided to put a 90/90 set up on my car (only thing I changed) and now it is dynoing 430/390 on the same dyno 
We have changed plugs (old ones looked fine), changed the MAF (had the Nx Maf ends on there... ruled that out), put a vacuum gauge on the intake and that passed
We also put it on the 1/4 mile simulater and it went from 123.5 mph to 121.... so there is definatly a power loose somewhere....
I have NO FREAKING idea what would cause me to LOOSE HP with upgrading my intake/tb
ANY ideas?
We have changed plugs (old ones looked fine), changed the MAF (had the Nx Maf ends on there... ruled that out), put a vacuum gauge on the intake and that passed
We also put it on the 1/4 mile simulater and it went from 123.5 mph to 121.... so there is definatly a power loose somewhere....
I have NO FREAKING idea what would cause me to LOOSE HP with upgrading my intake/tb
ANY ideas?
TECH Addict
Joined: Jun 2005
Posts: 2,660
Likes: 14
From: England
What about the a/f and timing did these change at all, or did you optimise them for the new setup?
I don't have any answer and in all honesty it's a bit beyond me. But the only thing I can think of is that maybe the 78mm intake was not a restriction and by adding more air flow into the engine it has upset something.
Also remember rolling road dyno's can vary so although there may be anohter issue don't rule out just a different dyno reading attributing to some of it. Tyre pressure, wheel balance or a worn bearing could easily afftect rwhp also.
I don't have any answer and in all honesty it's a bit beyond me. But the only thing I can think of is that maybe the 78mm intake was not a restriction and by adding more air flow into the engine it has upset something.
Also remember rolling road dyno's can vary so although there may be anohter issue don't rule out just a different dyno reading attributing to some of it. Tyre pressure, wheel balance or a worn bearing could easily afftect rwhp also.
TECH Addict
Joined: Jun 2005
Posts: 2,660
Likes: 14
From: England
def sounds a little odd.
What are your other mods and are you still stock 346ci??
I have heard similar things in the past with people putting to big carbs on engines. It's pretty common here in the UK with the 3.5 Rover V8, people add a massive carb and it makes less power than people with a smaller one because it's better matched to the setup.
Either that or there's some other underlying issue. I suppose logically the only way to find out if it's soley the intake/tb is to slap it back on the dyno and get a couple of good readings them swap out the intake for the 78mm setup and re-dyno it the same day. This will give you the best like for like.
It will also confirm if it is the intake that's causing the HP drop.
What are your other mods and are you still stock 346ci??
I have heard similar things in the past with people putting to big carbs on engines. It's pretty common here in the UK with the 3.5 Rover V8, people add a massive carb and it makes less power than people with a smaller one because it's better matched to the setup.
Either that or there's some other underlying issue. I suppose logically the only way to find out if it's soley the intake/tb is to slap it back on the dyno and get a couple of good readings them swap out the intake for the 78mm setup and re-dyno it the same day. This will give you the best like for like.
It will also confirm if it is the intake that's causing the HP drop.
Originally Posted by 300bhp/ton
def sounds a little odd.
What are your other mods and are you still stock 346ci??
I have heard similar things in the past with people putting to big carbs on engines. It's pretty common here in the UK with the 3.5 Rover V8, people add a massive carb and it makes less power than people with a smaller one because it's better matched to the setup.
Either that or there's some other underlying issue. I suppose logically the only way to find out if it's soley the intake/tb is to slap it back on the dyno and get a couple of good readings them swap out the intake for the 78mm setup and re-dyno it the same day. This will give you the best like for like.
It will also confirm if it is the intake that's causing the HP drop.
What are your other mods and are you still stock 346ci??
I have heard similar things in the past with people putting to big carbs on engines. It's pretty common here in the UK with the 3.5 Rover V8, people add a massive carb and it makes less power than people with a smaller one because it's better matched to the setup.
Either that or there's some other underlying issue. I suppose logically the only way to find out if it's soley the intake/tb is to slap it back on the dyno and get a couple of good readings them swap out the intake for the 78mm setup and re-dyno it the same day. This will give you the best like for like.
It will also confirm if it is the intake that's causing the HP drop.
I have an ARE 347 shortblock w/ forged pistons, Ported 5.3 heads and a big stick...
I have already sold the intake that I used before but I might borrow that for the comparison. It might vary well be that the 90/90 is too much for the set-up but the cam is 240's/250's cam and one would think it would need all the air it can get.
I was just trying to get an idea of others problems before I go and pull the valve covers and retorque the heads down and adjust the rockers again
Originally Posted by No Juice
Did you put the 78mm back on? try that first and see what it does
Were these back to back same day?
Were these back to back same day?
No, the pulls were on different days. I put the car on Sunday night and Wed night and it was exactly the same.
Trending Topics
The big intake might change the velocity (same
as going to heads w/ too large a volume) but you
would think this would favor top end HP while
taking away from midrange torque. Can you post
the before & after curves to see how the shape
was affected?
It seems like the tune is perhaps not truly
"optimized" as there is lost HP/TQ. I would not
dismiss that out-of-hand. If indeed the FAST is
delivering you more air you may want a different
AFR target now (having more top-end cylinder
pressure) or different spark (ditto). What do
the logs tell you about things like engine airflow,
MAP, knock retard etc. before/after?
as going to heads w/ too large a volume) but you
would think this would favor top end HP while
taking away from midrange torque. Can you post
the before & after curves to see how the shape
was affected?
It seems like the tune is perhaps not truly
"optimized" as there is lost HP/TQ. I would not
dismiss that out-of-hand. If indeed the FAST is
delivering you more air you may want a different
AFR target now (having more top-end cylinder
pressure) or different spark (ditto). What do
the logs tell you about things like engine airflow,
MAP, knock retard etc. before/after?
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bigger but not better 
Originally Posted by DEEZ98Z
I have an ARE 347 shortblock w/ forged pistons, Ported 5.3 heads and a big stick...
I have already sold the intake that I used before but I might borrow that for the comparison. It might vary well be that the 90/90 is too much for the set-up but the cam is 240's/250's cam and one would think it would need all the air it can get.
I was just trying to get an idea of others problems before I go and pull the valve covers and retorque the heads down and adjust the rockers again
I have already sold the intake that I used before but I might borrow that for the comparison. It might vary well be that the 90/90 is too much for the set-up but the cam is 240's/250's cam and one would think it would need all the air it can get.
I was just trying to get an idea of others problems before I go and pull the valve covers and retorque the heads down and adjust the rockers again
what do your heads flow that could be an issue also bigger is not always better IMO but a ls6 intake should dam if i was in the states i would buy that 90/90 for my motor and give u my ls6 intake but im in IRAQ AGAIN 
GOOD LUCK 
I agree, I would put the loss more on the Dyno then anything else. The 90's on your setup will DEFINITELY provide more power. But if you could, swap out and see what happens. But honestly, it's gotta be something in the tune IMHO. I've never seen a FAST 90 lose power, esp to a 78mm.
Best of Luck!
Adrian
Best of Luck!
Adrian
Originally Posted by jimmyblue
The big intake might change the velocity (same
as going to heads w/ too large a volume) but you
would think this would favor top end HP while
taking away from midrange torque. Can you post
the before & after curves to see how the shape
was affected?
It seems like the tune is perhaps not truly
"optimized" as there is lost HP/TQ. I would not
dismiss that out-of-hand. If indeed the FAST is
delivering you more air you may want a different
AFR target now (having more top-end cylinder
pressure) or different spark (ditto). What do
the logs tell you about things like engine airflow,
MAP, knock retard etc. before/after?
as going to heads w/ too large a volume) but you
would think this would favor top end HP while
taking away from midrange torque. Can you post
the before & after curves to see how the shape
was affected?
It seems like the tune is perhaps not truly
"optimized" as there is lost HP/TQ. I would not
dismiss that out-of-hand. If indeed the FAST is
delivering you more air you may want a different
AFR target now (having more top-end cylinder
pressure) or different spark (ditto). What do
the logs tell you about things like engine airflow,
MAP, knock retard etc. before/after?
The tuner tried more fuel, less fuel, more timing, less timing etc and where ever it made the most power is wheere we ende up at. I will try to get the infor of the airflow/map etc and post it up.
Changed from ported TB and LS6, to 90/90 setup and picked up 17 HP up top. Lost nothing down low! At about 4500, the 90/90 begins to shine! Both # SAE corrected and on the same dyno! Stock block, CNC heads, 228/230 cam!
