Self Tuning With SCT Pro Racer

[03cobra#2]

Without a vacuum source the bypass won't open. He'll need to lock it open somehow.Malcolm went through something like this. You need the lighter bypass spring so you don't get surge. Although I don't remember if he was able to totally get rid of the surge. It had to do with the sudden rush of air.

I have the lighter spring. Starting in a certain year Whipple moved to a lighter spring.

I read Malcolm's post and he had idle problems with the heavier spring. When he went to the lighter spring idle was good but the transition to boost was causing symptoms exactly like what I'm having. His solution was to put a restrict (nitrous jet) in the vac line to the solenoid so the bypass wouldn't snap open. Since I don't have that option I'll try a spring on there to counteract the light spring pressure.

My Whipple instructions say the bypass is designed to open with only 1" of vacume.

Edit: I appreciate everyone's input so far!

 

[cj428mach]

Without a vacuum source the bypass won't open. He'll need to lock it open somehow.Malcolm went through something like this. You need the lighter bypass spring so you don't get surge. Although I don't remember if he was able to totally get rid of the surge. It had to do with the sudden rush of air.

Yep, I posted it in his other build thread as a warning before he did cams, advise wasn't followed. Malcolm fixed it by going with smaller cams and redegreeing them.

 

[JAJ]

Without a vacuum source the bypass won't open. He'll need to lock it open somehow.Malcolm went through something like this. You need the lighter bypass spring so you don't get surge. Although I don't remember if he was able to totally get rid of the surge. It had to do with the sudden rush of air.

You're right of course! I think I zip-tied mine open, now that I think about it. I remember doing something to stop it from moving so I could datalog.

 

[03cobra#2]

Yep, I posted it in his other build thread as a warning before he did cams, advise wasn't followed. Malcolm fixed it by going with smaller cams and redegreeing them.

I went through and ready Malcolm's threads as he was having boost bypass problems with his cams.

I have plenty of vac at idle, 13-14"... more than enough to hold the bypass open. That's not the issue. I THINK the issue is when the bypass is closing its not a smooth easy transition but it is quickly snapping shut at part throttle. Malcolm had the same issue after he installed the bypass with the lighter spring. Issue was still there after he swapped / redegreed cams. He resolved the issue by putting a nitrous jet in his vac line to restrict flow to the solenoid. It eased the open to close transition.

Sent from my Pixel 2 XL using Tapatalk

 

[01yellercobra]

My son keeps trying to get me to put cams in my car because "it'll sound awesome dad!". But I like being able to take off smoothly in traffic.

 

[03cobra#2]

It's always a risk. I had comp stage 3 cams in my 2v back in the day not even degreed and the car drove / ran great. Obviously the supercharger complicates things.

Im not convinced the issue I'm having is cam related though. Start up, idle, low speed driving is great. I can get the car to take off, and accelerate smoothly no problem.....but I have to drive around it when gently accelerating. I don't want to have to do that though. So I'll do a little testing with this and see what I come up with.

Sent from my Pixel 2 XL using Tapatalk

 

[c6zhombre]

It's always a risk. I had comp stage 3 cams in my 2v back in the day not even degreed and the car drove / ran great. Obviously the supercharger complicates things.

I was under the impression it's not just the blower complicating things....but the extra 2 cams 4v vs the 2v. That blower might very well be an issue too, tho.

I know Kevin (04sleeper) has tuned cam'd terminators and they have behaved well.....and he's also quite possibly tuned more E85 terminators than other person on the planet....but having said that, he's always pretty much advised me to avoid considering cams as a mod because the negatives tend to outweigh the positives

If you just keep hitting a wall and can't quite figure this out to your satisfaction regarding drivability, you might try and contact him

 

[03cobra#2]

Update, finally some progress in the right direction.

First thing I did was start the car let it warm up and see where my vac is at idle. At 875 rpm or so it's at 11-12in of vac. Boost bypass is fully open and not fluttering. I even tried to close it while the engine was running and couldn't. So plenty of vac at idle to keep the bypass open. No problem there.

Next I took the car for a spin watching my boost / vac gauge the whole time. What I noticed is light part throttle acceleration 1500-2000 rpm when the gauge is showing vac and approaches 0 you get the surge and the wideband shows a temporary lean spike. I believe that's the boost bypass snapping shut at the last second right before boost (0 on the gauge) and a rush of air going in the engine causing the lean spike. With such a big blower and pullied for 26lbs it does not take much pedal effort at all to get right into boost, like 15 TP counts on my log.

My thought is if there is more spring pressure in the bypass valve it can close at say 4-6in of vac instead of 1-2in hopefully closing before any boost builds up. So my solution was to install a spring on the arm of the boost bypass to help pull it closed sooner. My thinking is that during part throttle low rpm acceleration the bypass will start to close at say 3-4in instead of 1-2in hopefully smoothing out the transition.

I went to home depot bought a variety pack of springs and picked one out that I felt was right. Installed it on the arm of the bypass valve and attached the other end to the fuel rail bracket. In essence giving the bypass more tension in the closed position.

Started up the car and let it warm up and idle at 875 or so rpm with about 11i-12in of vac. Checked the bypass and it was locked open, could not close it with my finger. So still more than enough vac to keep it open at idle. Blipped the throttle and it closed. Took the car for a spin and did notice the surge was decreased... Definetly better. The surge I noticed on my boost / vac gauge is happening sooner meaning the bypass is closing sooner... so the spring I put on there is working as intended. Vac to boost transitions at 2000 rpm and up is smoothed out and finally I feel like I'm heading in the right direction with this hiccup.

Low speed drivability and idle is good to go. I will probably hunt around for a stronger spring and put it on there in hopes to cure the problem all together. Doing research it's a common problem. Whipple even came out with a fix (putting orafice in vac line to solenoid for some guys). I'm not sure if it's the cams, the fact it's pullied for 26 lbs or what but at least I know what's going on and have improved things. At this point I'm happy with how it drives, and look forward to enjoying the car now and getting some more dyno numbers now that I can get my iats lower with ice.

Don't mean to ramble but I figure someone will run into this.

Sent from my Pixel 2 XL using Tapatalk

 

[01yellercobra]

Seems backwards to me. By putting the second spring on you're basically going back to the stiffer diaphragm right? But hey, if it works it works.

 

[03cobra#2]

Seems backwards to me. By putting the second spring on you're basically going back to the stiffer diaphragm right? But hey, if it works it works.

Exactly. After reading through Malcolm's posts back when, that was his final solution. Going to a stiffer diaphrahm and redegreeing the cams for more vac at idle.

Edit: i have acceptable vac at idle so just needed to stiffen up the diaphragm.

 

[03cobra#2]

Little update, doubled up on the spring I installed on the boost bypass to give more closing pressure, and the surge is significantly reduced, and I can say all but gone....still there a little. Had a nice drive into work with the car. So with my particular combo I am definitely benefiting from a boost bypass with a stiffer spring. YOu can tell the bypass opens well before my boost / vac gauge hits 0, lessening the surge of air into the motor. I did open a case with whipple to see what they say.

I filled up with E85 today, and noticed the car is running slightly lean. Tested and its testing out at 85%. Looks like I need to add a bit of fuel across the board. Last time I checked it was testing out at 80%. Looks like my area is finally onto the summer blend. I'll probably just add like 5% to the entire maf curve.

 

[Wings65288]

So when you go into boost the bypass OPENS? I was playing with that the other day when I tightened it down and was doing some test fitting with the inlet, I was trying to figure out the function of it.

 

[03cobra#2]

So when you go into boost the bypass OPENS? I was playing with that the other day when I tightened it down and was doing some test fitting with the inlet, I was trying to figure out the function of it.

Open at idle / vac and closes when you get into boost. If the closing transition does not happen smoothly or at the right time you can get a surge / drivability problem.

Sent from my Pixel 2 XL using Tapatalk

 

[can04cobra]

Have you considered trying the L&M bypass? It worked well for my combo on pump gas with comp stage 3 cams. I had issues of surging and bucking when driving and rpm was below 2200. Tip in was horrible even with the whipple lighter spring actuator. With the L&M it's a dream to drive. My car is making 730rwhp with a 2.9 whipple on 18lbs of boost.

Sent from my SM-G960W using the svtperformance.com mobile app

 

[03cobra#2]

Have you considered trying the L&M bypass? It worked well for my combo on pump gas with comp stage 3 cams. I had issues of surging and bucking when driving and rpm was below 2200. Tip in was horrible even with the whipple lighter spring actuator. With the L&M it's a dream to drive. My car is making 730rwhp with a 2.9 whipple on 18lbs of boost.

Sent from my SM-G960W using the svtperformance.com mobile app

I'll maybe give them a call. I'm satisfied where it's at now.

Sent from my Pixel 2 XL using Tapatalk

 

[03cobra#2]

Car is running great now. Got the chance to log a couple wot pulls today. I did notice I'm still not hitting max spark. My tables are set to ramp up to 21* by 6500 and I'm only seeing 18. My Iat2's were 142-143 at the end of the pull... My tune is set up to start pulling at 150 degrees. Any ideas on what I can look for?

 

[03cobra#2]

Dug around online and found this fantastic post explaining how the iat2 retard table works. The post basically says that when Iat2's reach 150 degrees it's pulling roughly 4 degrees of timing. The thing I didn't realize is that at 101 degrees timing is starting to get pulled and ramps up. By 150 degrees you have 4* of timing being pulled. Then the hotter you get the more timing gets pulled from there. Looking at my datalogs this is exactly what is happening. At least I know lol

Anyone change the values on their act retard tables?

Sent from my Pixel 2 XL using Tapatalk

 

[HPLouis]

I changed the values but these aren't the only changes I made to spark or temps.

Spark Retard for ACT
TEMPS MODDED Stock
254.000 -112.000 -160.000
200.000 -70.000 -100.000
150.000 -30.000 -60.000
100.000 0.000 0.000
-256.000 0.000 0.000
-256.000 0.000 0.000
-256.000 0.000 0.000

It's a multiplier so I'm pulling less timing for the temps but I adjusted my base spark tables, MBT, A/F and temp tables to account for this and give me more control over my temps and timing.

 

[03cobra#2]

I changed the values but these aren't the only changes I made to spark or temps.

Spark Retard for ACT
TEMPS MODDED Stock
254.000 -112.000 -160.000
200.000 -70.000 -100.000
150.000 -30.000 -60.000
100.000 0.000 0.000
-256.000 0.000 0.000
-256.000 0.000 0.000
-256.000 0.000 0.000

It's a multiplier so I'm pulling less timing for the temps but I adjusted my base spark tables, MBT, A/F and temp tables to account for this and give me more control over my temps and timing.

Thanks for sharing! So did you go a bit lower on the spark tables? Did you make adjustments to the ect retard table?

I was thinking of doing something similar since I'm on E85.

Sent from my Pixel 2 XL using Tapatalk

 

[HPLouis]

I added +3 midrange for timing but lowered it all by 1 degree up top. I'm also stock so I have more room to play with. When I was pullied, the timing was lower since I had less margin for error.

I did lower all my ECT temps by 10 degrees, installed 1 temp range colder spark plugs and added +0.2 fuel in my A/F across the top. I also lowered the turn on temps for my intercooler pump by 20 degrees.