Cam questions

[KaiPL]

I just got my Gen III back from a local shop.

Here is what I had done:

ported heads Flow: .288 @ .550 and .301 @ .600
Compression ratio 9.9:1
Manley severe duty valves 2.055 intake 1.6 exhaust
Manley dual springs and titanium retainers
Crower custom cam 224/228 @.050 .585/.585 lift with 1.7 Rockers LSA 113
Jesel roller rockers (1.7)
Manley chrome-moly pushrods
Valve cover spacers
VEC 2

I already had Billy Boat stepped (1 5/8 to 1 3/4) headers, high flow cats, and a Corsa track exhaust with cross-over delete.

The results on the dyno were o.k., but not quite as good as I was hoping for. I gained some high end hp and torque, but lost a substantial amount of low and mid-range hp and torque. Here's a dyno graph: The new results are in red (hp) and purple (tq). I am wondering what I might do to claw back some of the low and mid range numbers, and generally improve area under the curve here.

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First off, I am going to work on some additional timing and fuel tuning with the VEC2.

If that doesn't accomplish anything, I may have a look at my cam.

My current cam has a duration of 224 on intake, and 228 exhaust. That is compared with 212 intake and 232 exhaust for the stock cam (measured at .050.) The lobe separation angle is 113 degrees (don't know the lsa for the stock cam.)

Lift (with the 1.7 rockers) of the new cam is .585 for both intake and exhaust (compared with .544 for the stock cam.)

The one thing that jumps out at me on the new camshaft is that the exhaust duration is lower than that of the stock camshaft.

Out of curiosity, I checked out Crower's stage 3 camshaft they sell for the Gen III viper. The specs for the Crower stage 3 shaft are 238 duration for both intake and exhaust, and lift of .587 for both intake and exhaust. Their stage 2 camshaft has 230 duration, and .558 lift.

Here's a comparison of my cam, the stock cam, and the three Crower cams available:

--- ---- duration --- lift
Mine: 224/228 -- .585/.585
stock: 212/232 -- .544/.544
st 1: 222/230 -- .563/.558
st 2: 230/230 -- .558/.558
st 3: 238/238 -- .587/.587


Any thoughts?

 

[Schulmann]

The cam that you have is designed for higher RPMs (primarely race use) to provide more torque above 4000rpm. It is "normal" that you loose torque below 4000rpm.

What is the overlap on these cams ?

The numbers that you get are very decent.
Likely you have a good car for drag races.
I am curious to know how it drives on the street.

Often people upgrade the cam to get higher HP numbers but they forget that 99% of the time they ride on the street.


Do you have your AFR chart logged ?
Can you upload the chart of your fuel and ignition map used in the vec2 program ?

With a good race fuel maybe you can ran an agressive timing and pickup some torque.

 

[HOdbleFman]

Kai, I wouldn't say your cam is too large. I wouldn't think you would lose that much low end because of that cam. I changed cams in my car and went with a much larger cam than that last summer. I was having a severe low end power loss. At first I thought maybe I went too big, but I took the VEC2 off the car and I got some of my low end power back. I never could figure out the cause, but 50 ft.lbs seems like a lot to lose by just stepping up to a mild cam. It's pretty simple to unhook the VEC2, so maybe try removing it and making a few runs on the stock computer. I know for a fact that the cam you installed is not too big to run with the stock computer. I don't know who did your install, but it's important that when you re-install the cam sensor that you don't get it too close to the cam gear. On my second install I got it too close and took the nose of the sensor off. It caused some funky running of the car. These are just some ideas that you may want to check out.

 

[Schulmann]

In fact you don't need to remove the VEC2.
You can just write a program where all the values are set to zero. I think such an exemple even comes with the CD-kit.

If the VEC2 program reduces your torque it means that you tuned it into the wrong direction.

But post your VEC2 prog and you can get some comments on it.

 

[99 R/T 10]

I have to ask, where did you get the Valve cover spacers

 

[HOdbleFman]

No, unhook the VEC2 completely. I know theoretically zeroing all the settings should have the same effect, but for some reason on mine it didn't.

 

[KaiPL]

I have to ask, where did you get the Valve cover spacers

I got the valve cover spacers from Crower. They are very nice, beautifully machined out of billet aluminum.

I will post VEC2 fuel and ignition maps tonight.

Thanks everyone for the input. I really appreciate it.

Can anyone tell me why a low exhaust duration on my cam would be a good thing? I would think that one would want the exhaust duration to be at least as high as that of the stock cam.

 

[GTS Dean]

I'm looking at the barometric pressure readings during your dyno runs. 24.61" Hg and a 1.27 CF?????????? Was this during a tornado, or what?

edit: I just checked your web page and see that you're from Boulder, CO. Makes more sense. I somehow thought you were from Kali.

 

[Fast Freddy]

the cam and the headers are holding you back. ditch that cam for a comp coupe cam. get a set of bellanger headers that have 1-3/4 primaries. also i would have had my compression ratio raised to at least 10.0:1. i believe you can actually raise your compression ratio up to like 10.2:1 and still run on premium pump gas. its all in the tune. west coast vipers in cali has the software to manage it all. i believe they use aem or something like that. whatever they use is supposed to be the best. it will get you a better A/f ratio than anything currently available on the market from what i understand. you should be looking at 525 rwhp and close to 575 rwtq with this setup. i will be taking my car into them come february to get those mods done. their heads have similar valve sizes to yours and are cnc ported and polished. i am not sure but i think they have similar flow characteristics as your heads too. i am gonna have them install their heads on my car too. i will be using 1.7 ratio T&D roller rockers. whose heads are you runnin?

 

[KaiPL]

Here's my VEC2 tune characteristics:

Fuel and RPM:

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Fuel and Manifold Pressure Load

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Ignition and RPM:

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Ignition and Load (2 pictures, one showing low load numbers, the other high.)

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[KaiPL]

I realize that 1-3/4 would flow better than stepped 1-5/8 to 1-3/4. The exhaust restriction is one of the reasons why I wonder if the relatively short exhaust duration on my cam is a good thing. Does anyone know the characteristics of the Comp Coupe cam? Idealy, I would have had the work done by West Coat Viper. Trouble is that I live in Colorado, which is far away from WCV, and also I wanted the work done sooner than WCV could do it, so I could get the car modded before the track season ended here. I've seen the dyno charts for cars from WCV, Heffner, etc. that have had similar work done, and the power and torque curves are all significantly better than where I'm at right now. The head work was done by a local shop, the same shop that did the cam, valves, etc. They are called Dragon Race Engineering. They specialize in Corvettes, and have a pretty good reputation for Vette tuning. I know a number of people that have n/a Vettes that they have tuned that are really strong.

the cam and the headers are holding you back. ditch that cam for a comp coupe cam. get a set of bellanger headers that have 1-3/4 primaries. also i would have had my compression ratio raised to at least 10.0:1. i believe you can actually raise your compression ratio up to like 10.2:1 and still run on premium pump gas. its all in the tune. west coast vipers in cali has the software to manage it all. i believe they use aem or something like that. whatever they use is supposed to be the best. it will get you a better A/f ratio than anything currently available on the market from what i understand. you should be looking at 525 rwhp and close to 575 rwtq with this setup. i will be taking my car into them come february to get those mods done. their heads have similar valve sizes to yours and are cnc ported and polished. i am not sure but i think they have similar flow characteristics as your heads too. i am gonna have them install their heads on my car too. i will be using 1.7 ratio T&D roller rockers. whose heads are you runnin?

 

[KaiPL]

MOPAR's "race" cam

Cam lift = 0.544 for both intake and exhaust.
Duration is 220.00 Intake, 230.5 Exhaust.

Is this the same as the Comp Coupe cam?

 

[Dave R]

Based on your fuel load table, you are only reducing stock fuel amounts (all negative "ms" amounts); nowhere are you increasing fuel. During WOT (approx 4V-5V), all your values are set to zero, effectively running the stock fuel map.

 

[KenH]

I agree with Dave R. You are basically running the stock fuel map at WOT and less than a degree of ignition advance over stock. Doesn't seem like the VEC2 is being put to much use. Definitely need to post an A/F log if possible to see if the VEC2 programming needs to be modified.

 

[Schulmann]

Yes your program looks very strange.
Both fuel and ignition maps are odd.
Espetially fuel looks like not doing anything.

There is place for a lot of improvement.
Who did write this program ?

 

[KaiPL]

Yes your program looks very strange.
Both fuel and ignition maps are odd.
Espetially fuel looks like not doing anything.

There is place for a lot of improvement.
Who did write this program ?

The shop that did the head, valve, and cam work wrote this tune program.

On Monday, I'm taking the car to a different shop for some additional dyno-tuning. Hopefully, they can do better. If I can solve my problems with some tuning, and don't have to mess with the cam, I will be happy.

 

[Schulmann]

KaiSRT10,

The best thing would be in your case to contact Sean Roe.
He might be able to write a personalized program.

 

[Joseph Dell]

We didn't see the "fuel options" tab... so we don't know if he is running bigger injectors than stock. that would explain the fuel coming out of the car from the VEC2. Can you post that 3rd fuel tab?

JD

 

[Dave R]

What we really need to see is the air/fuel ratio associated with the dyno pulls; that will tell the real story.

As far as the negative fuel values, these are being applied during idle and normal driving conditions.

 

[KaiPL]

I blew up my engine today at the track.

Lots of smoke, fire, and oil.

I'm bummed.

 

[Fast Freddy]

wow! that ***** Kai. i am sorry to hear this. so do you think you were detonating as a result fo bad timing and A/F ratios or was it a mechanical failure? what track were you racing at and what was the elevation? i am assuming you were road racing. colorado is a high elevation and you tuner has surely altered your A/f ratios to acommodate this. i am guessing he didn't have the tune right?

 

[KaiPL]

Yes, I was road racing.

I was coming down the straight, and the car began to shudder. I thought I had blown a tire. I slowed to a crawl and checked my tire pressure monitor. Pressure was fine for all the wheels. I then noticed that the car was losing power. I checked my gauges. Oil pressure,oil and water temperature were normal. No check engine light. I exited into the pits, and my engined stopped running as I pulled into my parking spot.

I got out of the car, and noticed that there were flames coming out of my driver's side exhaust. I put the fire out by spraying my fire extinguisher up into the side pipe. Engine compartment looked normal. There was some oil dripping on the ground, but I couldn't tell where it was coming from.

I checked the air fuel mixture from the dyno runs, and it ranged from 10.9 to 12 up to 5000rpm, and 12 to 12.6 from 5000 to 6000. Things may have become too lean in the upper range and detonated.

The car is still sitting in my garage. They guys who did the work on it are at the SEMA show and won't be back until next week.

I'm seriously bummed right now.

 

[Joseph Dell]

Kai -

I'm sorry to hear about your car troubles. fire in the exhaust = unburnt fuel. I've had this happen before. Yeah, 12.0 to 12.6 is lean on a blower car but should be OK on a N/A car. You may be perfectly fine... just may need a plug change and off you go. have you done any other diagnosis? Or is the car going back to dodge for some "warrantee" work?

JD