dyno numbers to low? (bhp)

Hey there guys.
I went to a dyno to see what kind of numbers the car has to offer.

The mods on the car are as followed:
1999 GTS
20.000 miles

Heffner tuned with:
Headwork
Heavy duty valve springs
Stainless steel valves (2.02 intake and 1.60 exhaust)
Titanium valve retainers
1.7 T&D roller rockers
Alu flywheel
Smooth tubes
Modified airbox with K&N panel filters
70mm TB’s
Magnecore wires
Full B&B exhaust (headers/catback/high flow cats)
Crower Comp cam (stage 2 int 275/exh 284)
Vec II with roe racing map
3,55 gearing

It was on a Dynojet and the run was done in 5th gear and only to 5500RPM, because I wanted to keep everything safe. (will 500 RPM more make a big difference?)

I was a little surprised in a bad way that the car only made 471 RWHP, but was thrilled to see the Torque 735,9 Nm

When I correct the numbers to usa specs:
RWHP 471,1 @ 5433
RWTQ 542,9 @ 4157

So what do you guys think of those numbers????

I live in the Netherlands and tuning a viper is really hard over here, because I've a hard time finding someone capable of tuning the Vec II. Am thinking of going for a roe charger in the near future, but first need someone who is capable of helping me tuning it.

Dynosheet:


No movie of the dyno yet since my camera broke down when WOT. But this is the car:
http://www.youtube.com/watch?v=MJ6cnX8fQYc

yes, seems low, the TB's are not helping and you used the wrong gear....use 4th

plumcrazy said:

yes, seems low, the TB's are not helping and you used the wrong gear....use 4th

Click to expand...

Agreed, the 3.55 gearing doesn't help either.

The larger TB are only beneficial if you are force fed. So when you add your Roe blower it will help.

What will a pull in 4th gear and smaller TB's bring to the table do you guy think??

And what kind of numbers do I need to see with my mods??

GTSnake said:

Agreed, the 3.55 gearing doesn't help either.

The larger TB are only beneficial if you are force fed. So when you add your Roe blower it will help.

Click to expand...

In what way are the 3.55's hurting his numbers? Wouldn't the tech just set the dyno to 3.55 gearing?

Nut
I have very similar mods to yours. However, I have stock gears and I'm not sure how my Comp Cam compares to your Crower. Compression ratio on my heads (Greg Good)is 10.5:1 instead of the stock 9.5:1. I've dyno'd 540whp and 575tq. This was the same dyno that gave me 390hp before my mods. I've only made a couple of passes at the track. I hit the rev limiter in 1st but still ran a 11.31 @ 126mph (1.71 60') - in crappy Oklahoma air. The MPH seems to confirm the dyno.

I think you can find some more power in your engine. Use 4th gear. Also, my engine seemed to like a little more timing. I ended up adding 4 degrees at 4k rpm. IIRC, timing alone gave me an extra 20 hp at the top. Hope that helps.

Thanks for the advice.

I also been in contact with DP-engineering overhere and they are capable of mapping the VECII. Will attend there shop in a short while for a dynorun. They use one where the wheels have to come off.

Then I will sort everything out this winter and let them tune my car in the beginning of 2011. There's def. room for improvement.

Nutkees, you wouldn't have the cam-specs handy would you?

Before you do any tuning, go back and do the run in 4th. That is going to be your biggest problem. Make sure the normal stuff is configured; especially if it is a load bearing dyno (input weight, gearing, etc). I would think that a pull in 4th would get you closer to the numbers you should have. Or, if the dyno is out of the question, take it to a 1/4 mile track...your trap speed will be a good telling of what kind of power you are making.

Tagoo, I am a little surpirsed that your car was trapping 126 with the stock gearing. With your power levels and N/A, I would think it would be over 130 easily. Are you up in some altitude out there in OK?

nutkees said:

Thanks for the advice.

I also been in contact with DP-engineering overhere and they are capable of mapping the VECII. Will attend there shop in a short while for a dynorun. They use one where the wheels have to come off.

Then I will sort everything out this winter and let them tune my car in the beginning of 2011. There's def. room for improvement.

Click to expand...

You are running very lean at peak torque, it looks like 13.7. You want them to flatten that curve so that you are running approximately 12.5 a/f. You can be a little fatter (12.2 at peak torque. The a/f looks fine at peak hp.

You are not going to see a huge drop off due to the 3.55's however, using 5th gear will throw larger losses into the equation. Your set up should show 525-550 if the engine is mechanically sound. What is most surprising that your hp peaks at 5300, that would normally indicate no head work or aftermarket cam. This may be simple, but, something as simple as misadjusted throttle cables or a floor mat under the pedal can reduce your hp.

nutkees said:

Thanks for the advice.

I also been in contact with DP-engineering overhere and they are capable of mapping the VECII. Will attend there shop in a short while for a dynorun. They use one where the wheels have to come off.

Then I will sort everything out this winter and let them tune my car in the beginning of 2011. There's def. room for improvement.

Click to expand...

You are running very lean at peak torque, it looks like 13.7. You want them to flatten that curve so that you are running approximately 12.5 a/f. You can be a little fatter (12.2 at peak torque. You will pick up midrange power by adjusting the a/f. The a/f looks fine at peak hp.

You are not going to see a huge drop off due to the 3.55's however, using 5th gear will throw larger losses into the equation. Your set up should show 525-550 if the engine is mechanically sound. What is most surprising that your hp peaks at 5300, that would normally indicate no head work or aftermarket cam.

99VPRGTS
Yep I think I can do better than 11.3 @126. On that run, I hit the rev limiter pretty hard in first. Redline came so quickly it took me a second to process what had happened. I was pretty slow shifting into second. I'm really think I can do a 10.99 at 130ish if I can get a good clean run.

We have a lot of humidity here in OK. Elevation is about 1200', but it usually gets adjusted up to 3000' or so because of the air. I had pretty good weather when I dyno'd. Not as much at the track.

Sean Roe helped me learn how to tune the Vec. When I logged it he would write me a program to adjust timing and mixture and I could open the email, unzip and load it into my Vec with my laptop. I eventually got tired of being a PIA to Sean and started doing my own tuning and only use Sean for advice when it's necessary. There is several threads that include logging and instructions on how to tune with a vec. Guess you need to join the club to get acess to those threads? We also have a Vec tuning group where there are many people that understand the vec and would be happy to help you adjust your program.

Beyond that, there are some excellent Viper Tuners that help to sponsor the Club and they can do "Remote Tuning" over the telephone, believe it or not. If you're after perfection then, since you bought a car that needs tuning - you could fly a tuner over there to personally tune your car. You might want to get that tuner to go over in the winter and bring the blower with him, then tune your car before he leaves.

Macedo Motorsports and DC Performance are 2 that are willing to travel to help you out. Remote tuning is reliable and reasonably cheap. Hiring a tuner to fly there and do the work, then tune the car is the best way to do it.

Ummm, why didn't you buy a car that ran perfect or buy a tune before you took the car?

4th gear pull will get you 500 rwhp...100 rwhp over stock and about right for your mods

@rtttted

Bought the car because it is a nice example and there are not a lot of vipers overhere and def. not for this kind of money. Didn't know if I needed a tune because the car never been on a dyno before. Car runs just fine, but offcourse I want it to be perfect.

@ Jack B
Your saying that there is a possible that there is no head work done to the car and maybe running a stock cam? Is there a way to check this without messing with the engine??

@ Jack B

Can you tell me when I should have seen peak HP w/headwork and a cam? They could have revved the engine a little more to say 6000rpm, don't know if that will change anything in the numbers?

Was looking into my Ease software which I run during the dynotest.

In the playback I see that the Absolute Throttle position is only 80.4% at the most. I geuss that's a little to low?

Maybe you guys can see more info thats important?

nutkees said:

@ Jack B

Can you tell me when I should have seen peak HP w/headwork and a cam? They could have revved the engine a little more to say 6000rpm, don't know if that will change anything in the numbers?

Click to expand...

A car with RR and headers/exhaust should show 450-470. I believe mine dyno'ed 464 with exhaust and RR. That car with a cam and good head work should show peak hp closer to 5800-6000. The tune is going to be the variable. The dyno and dyno operator are also part of the equation.

nutkees said:

Was looking into my Ease software which I run during the dynotest.

In the playback I see that the Absolute Throttle position is only 80.4% at the most. I geuss that's a little to low?

Maybe you guys can see more info thats important?

You must be registered for see images attach

Click to expand...

That is a relative position reading, you were at wot.

Jack B said:

A car with RR and headers/exhaust should show 450-470. I believe mine dyno'ed 464 with exhaust and RR. That car with a cam and good head work should show peak hp closer to 5800-6000. The tune is going to be the variable. The dyno and dyno operator are also part of the equation.

Click to expand...

The next time I'm going on a dynapack 4000, where the wheels has to come of.

They also need to rev the car a little bit more. Last time was only to 5400 rpm, so maybe peak HP can still be @ 5800-6000

A new tune can def. get the car to run even better. I must say the car pulls like a charm. a 3-rotor rx-7 with 550bhp couldn't keep up.And they are a lot lighter.

Man I love this car!

Hey Kees,

atlantic sportscars in the Uk (james) has lots of experience installing Roe superchargers and tweaking your tune. He drives a supercharged 99 himself, he can help you out, but it's a drive to the UK, sounds like more fun as flying someone in...

Good luck

nutkees said:

The next time I'm going on a dynapack 4000, where the wheels has to come of.

They also need to rev the car a little bit more. Last time was only to 5400 rpm, so maybe peak HP can still be @ 5800-6000

A new tune can def. get the car to run even better. I must say the car pulls like a charm. a 3-rotor rx-7 with 550bhp couldn't keep up.And they are a lot lighter.

Man I love this car!

Click to expand...

One run was went to 5600, but, the power in both runs flattened at 5300-5400.