HP numbers aren't adding up!
Thread Starter
Instructor
Joined: May 2006
Posts: 150
Likes: 0
From: Jacksonville North Carolina
HP numbers aren't adding up!
So I installed an STS twin turbo system on my 02 Z, did the install myself. I took it into a shop to get it tuned and honestly i'm not really impressed with the numbers. I pulled 402rwhp without the tune and when the tune was finish I got 423rwph. I just think that there has got to be something wrong. Granted i'm only running 6psi, but STS is quoting 32 hp per pound of boost. I'm about 100rwhp lower than what STS is saying it should make.
I know that the tuners dyno kinda of "low *****" numbers but still, 100hp? Also, i know they didn't take off the filter covers that i told them to do but i figured that should starve it of any more than 20hp but i could be wrong. Also, I don't know if this matters or not but i noticed when it was on the dyno, it wasn't really sitting on top, the rear wheels were kind of on the back side of the roller. Could that make a difference?
Any input would be great guys, thanks!
I know that the tuners dyno kinda of "low *****" numbers but still, 100hp? Also, i know they didn't take off the filter covers that i told them to do but i figured that should starve it of any more than 20hp but i could be wrong. Also, I don't know if this matters or not but i noticed when it was on the dyno, it wasn't really sitting on top, the rear wheels were kind of on the back side of the roller. Could that make a difference?
Any input would be great guys, thanks!
Le Mans Master
Joined: Mar 2005
Posts: 5,811
Likes: 31
From: Minnetonka MN
St. Jude Donor '06
whoa! thats really low... are you sure the system is actually pumping out 6psi of boost? do you have a boost guage installed?
who is your tuner? they should know why or what is going on by simply looking at the tuning tables...
do you have any boost leaks? all the piping clamps are tight??? you could loose boost easily if u have leaks. Especially with an STS kit b/c there are A LOT of possibilities of boost leak....
hope this helps.
Aj
who is your tuner? they should know why or what is going on by simply looking at the tuning tables...
do you have any boost leaks? all the piping clamps are tight??? you could loose boost easily if u have leaks. Especially with an STS kit b/c there are A LOT of possibilities of boost leak....
hope this helps.
Aj
Thread Starter
Instructor
Joined: May 2006
Posts: 150
Likes: 0
From: Jacksonville North Carolina
whoa! thats really low... are you sure the system is actually pumping out 6psi of boost? do you have a boost guage installed?
who is your tuner? they should know why or what is going on by simply looking at the tuning tables...
do you have any boost leaks? all the piping clamps are tight??? you could loose boost easily if u have leaks. Especially with an STS kit b/c there are A LOT of possibilities of boost leak....
hope this helps.
Aj
who is your tuner? they should know why or what is going on by simply looking at the tuning tables...
do you have any boost leaks? all the piping clamps are tight??? you could loose boost easily if u have leaks. Especially with an STS kit b/c there are A LOT of possibilities of boost leak....
hope this helps.
Aj
My tuner is Majestic Motorsports in Jacksonville, NC. He used HP tuners.
I'll have to check the pipes for leaks then cuz it just doesn't seem right to me. The tuner was telling me that it was a good gain cuz stock C5's he was getting in were running about 305 to the wheels, and once again that seems really low.
Race Director
Joined: Mar 2008
Posts: 12,413
Likes: 502
From: Rio Rancho NM
2 things
1: Check for boost leaks
2: Run it at the track don't get caught up in numbers. If it ran low 11's but only dynoed say 300 would you really care? I see guys get caught up in numbers all the time. See what she does and that will tell you what your making. Who knows maybe the dyno wasn't calibrated correctly, air temp was wacky, a duck crossed the street, it can be anything. Dyno numbers to me is just bragging rights. Tell me what you do at the track and then my interest gets peaked.
1: Check for boost leaks
2: Run it at the track don't get caught up in numbers. If it ran low 11's but only dynoed say 300 would you really care? I see guys get caught up in numbers all the time. See what she does and that will tell you what your making. Who knows maybe the dyno wasn't calibrated correctly, air temp was wacky, a duck crossed the street, it can be anything. Dyno numbers to me is just bragging rights. Tell me what you do at the track and then my interest gets peaked.
Le Mans Master
Joined: Feb 2007
Posts: 9,296
Likes: 1,531
From: Oviedo Florida
2024 C5 of the Year Finalist - Modified
2024 C2 of the Year Finalist - Modified
2023 C2 of the Year Finalist - Modified
2021 C2 of the Year Finalist - Modified
2016 C5 of Year Finalist
2 things
1: Check for boost leaks
2: Run it at the track don't get caught up in numbers. If it ran low 11's but only dynoed say 300 would you really care? I see guys get caught up in numbers all the time. See what she does and that will tell you what your making. Who knows maybe the dyno wasn't calibrated correctly, air temp was wacky, a duck crossed the street, it can be anything. Dyno numbers to me is just bragging rights. Tell me what you do at the track and then my interest gets peaked.
1: Check for boost leaks
2: Run it at the track don't get caught up in numbers. If it ran low 11's but only dynoed say 300 would you really care? I see guys get caught up in numbers all the time. See what she does and that will tell you what your making. Who knows maybe the dyno wasn't calibrated correctly, air temp was wacky, a duck crossed the street, it can be anything. Dyno numbers to me is just bragging rights. Tell me what you do at the track and then my interest gets peaked.
Try another tuner it couldn't hurt. The tuner you used should
of had alot of questions concerning your low numbers.
Le Mans Master
Joined: Mar 2005
Posts: 5,811
Likes: 31
From: Minnetonka MN
St. Jude Donor '06
stock C5's dyno 300-315 ish. do you have any other supporting mods? then yes, i guess the 120rwhp gain from bone stock would be about right.
i would def check all the hose connections and verify boost level. you should be there when the tuner is running this car, you need to know whats going on. i also suggest trying a different tuner. this one seems like he just wants to tune and get you out of the shop.
Aj
i would def check all the hose connections and verify boost level. you should be there when the tuner is running this car, you need to know whats going on. i also suggest trying a different tuner. this one seems like he just wants to tune and get you out of the shop.
Aj
Drifting
Joined: Aug 2008
Posts: 1,491
Likes: 1
From: Goldsboro NC
Well i haven't checked the boost level myself but i do have a boost gauge, so i'm sure the tuner read it correctly.
My tuner is Majestic Motorsports in Jacksonville, NC. He used HP tuners.
I'll have to check the pipes for leaks then cuz it just doesn't seem right to me. The tuner was telling me that it was a good gain cuz stock C5's he was getting in were running about 305 to the wheels, and once again that seems really low.
My tuner is Majestic Motorsports in Jacksonville, NC. He used HP tuners.
I'll have to check the pipes for leaks then cuz it just doesn't seem right to me. The tuner was telling me that it was a good gain cuz stock C5's he was getting in were running about 305 to the wheels, and once again that seems really low.
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Every 2027 Corvette Engine Explained
Joe Kucinski
Designer Imagines A Corvette That Looks More Like a Corvette Than the Corvette
Verdad Gallardo
10 Ugly Corvettes That We Still Kinda Love
Joe Kucinski
Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer
Brett Foote
10 Things Every Corvette Owner Needs (2026 Edition)
Michael S. Palmer
8 Most "Only Corvette Owners Understand" Quirks and Problems
Pouria Savadkouei
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years
Joe Kucinski
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!
Michael S. Palmer
Thread Starter
Instructor
Joined: May 2006
Posts: 150
Likes: 0
From: Jacksonville North Carolina
My boost guage is electrical and the tuner hooked it up from the sending unit to the brake booster line (which also goes to the wastegates and blow off valve). And there are no other mods done to the car.
Chicago1,
I completely agree with you, numbers don't mean anything and the track tells you what the car will acctually do. However, 100hp is a lot.
Chicago1,
I completely agree with you, numbers don't mean anything and the track tells you what the car will acctually do. However, 100hp is a lot.
Race Director
Joined: Apr 2009
Posts: 10,581
Likes: 252
From: SE TEX
That is where my boost gauge is hooked so it should read fine. I would confirm that you are seeing 6lbs of boost (may need a passenger to help with this). It should stay around 6lbs and not hit it and then drop as you get into the higher rpms. Also may wanna research threads in the Z06 specific section so see other results.
Le Mans Master
Joined: Oct 2005
Posts: 7,088
Likes: 1,829
From: Metro Detroit Michigan
Your dyno numbers may be fine.
Observing your own reaction, can you see why tuners and dyno operators may be tempted to "lean on the numbers" a bit, in order to not look worse than others who lean on the numbers?
If we keep this up, stock LS1 engines with5 pounds boost will soon be making 1000 hp.
Observing your own reaction, can you see why tuners and dyno operators may be tempted to "lean on the numbers" a bit, in order to not look worse than others who lean on the numbers?
If we keep this up, stock LS1 engines with5 pounds boost will soon be making 1000 hp.
Melting Slicks
Joined: Mar 2006
Posts: 3,448
Likes: 21
From: EARTH
Numbers are very low taking it to the track is not solving anything...
I made 510rwhp with 6psi and I have 8:5 compresstion.
Can you post dyno graph? whats the A/F Ratio?
Go test the car and take a look at the boost gauge!!
Any other mods on the car other than the turbos??
I made 510rwhp with 6psi and I have 8:5 compresstion.
Can you post dyno graph? whats the A/F Ratio?
Go test the car and take a look at the boost gauge!!
Any other mods on the car other than the turbos??
Racer
Joined: Nov 2008
Posts: 313
Likes: 1
From: Cypress, TX
Sounds low.
Check For Boost Leaks, and check to see if your even holding 6 psi till redline, you could be falling off (boost leaks, Wastegate problem) and this can cause you not to make peak numbers.
Check For Boost Leaks, and check to see if your even holding 6 psi till redline, you could be falling off (boost leaks, Wastegate problem) and this can cause you not to make peak numbers.
Le Mans Master
Joined: Aug 2005
Posts: 7,890
Likes: 0
From: FL
Dont go to the track, dont go to another tuner or even back to your tuner.
Like everyone said drive the car all the way through redline in say 2nd gear and make sure you have 6psi or close all the way to redline. It can't be and if it isnt you need to call your tuner and ask him how he missed that and go elsewhere after
your car should make 365rwhp stock right 10% loss of 405 hp?
So you picked up 60rwhp with a twin turbo kit?
Like everyone said drive the car all the way through redline in say 2nd gear and make sure you have 6psi or close all the way to redline. It can't be and if it isnt you need to call your tuner and ask him how he missed that and go elsewhere after
your car should make 365rwhp stock right 10% loss of 405 hp?
So you picked up 60rwhp with a twin turbo kit?
Tech Contributor
Joined: Apr 2007
Posts: 10,924
Likes: 78
From: Forney Texas
There are so many things that could cause this problem. You could have the PCM pulling timing due to many things. weak valve springs, boost leak, clogged exhaust, running on only one turbo, intake restricted.....the list goes on. It's certainly worth investigating.
Safety Car
Joined: Mar 2006
Posts: 4,448
Likes: 4
From: Sarasota Florida
St. Jude Donor '06
Take it to a GOOD shop with plenty of experience with FI Vettes. If you can't find someone closer, Virginia Speed in Virginia Beach is definitely qualified.
The shop/tuner you use is THE most important aspect to any FI build, imo.
The shop/tuner you use is THE most important aspect to any FI build, imo.
Racer
Joined: May 2009
Posts: 270
Likes: 1
From: Athens, Georgia
Hmm, intresting. My dyno was a little off i thought too. I have a cam(224/228xer)/headers,vararam setup only making 392rwhp/384rwtq on a dead on tune and i see 02 z's making 395whp with headers only.. Maybe the dyno reads low if everything checks out. If you can trap high 120s low 130s that should say you making ~500rwhp.
