Has anyone disconnected the VTec solenoid or retarded its operation to above redline to avoid the inherent dip and tuning problems. Esentially the second set of lobes is set up for high RPM NA which I am sure doesn't help when boosting.

 

 

no you would lose lots of power.to remove the dip you have to adjust the vtec point.messing with the timing and a/f also helps

 

it's difficult to alleviate altogether with a piggy back system. like auriel said the best way is to move your vtec point. the dip will still occur, but depending on the tune if it's in a different point in the powerband the effects may not be as bad.

the only way to get rid of the dip completely is to go standalone

btw auriel - how is the car running?!

 

That's a bad idea...

The second set of lobes helps a lot with efficient turbo setups and supercharged setups. You make more power sooner with a lower VTEC engagement.

The only time VTEC engagement loses power is with log style turbo manifolds and restrictive exhaust setups. These setups require VTEC to be moved significantly higher to prevent a loss in power.

It all comes down to pressure and the inertia of the fluid. With an efficient turbo setup, the bigger cam profile means that more air fuel mixture can enter the engine. With a log manifold, the bigger cam profile and additional overlap mean that exhaust gases don't efficiently evacuate the cylinder until the RPM becomes high enough that the effects of inertia cancel out the higher pressures caused by the more restrictive exhaust setup.

Tim

 

I can tell you that with a Test Pipe, the car pulls very hard in VTEC, unfortunately for the GREDDY people we have to have our CAT, and the difference is night and day..............

Is anyone running a HFC with the Greddy kit and is there Boost Creep issues?


Anyone have a surefire way to modify the Wastegate on the Greddy kit to prevent Boost creep, I am really itching to take my stupid cat out. I know the WHP difference is small but the sound alone (in vtec) is worth it

 

Not always. From what i've seen there can be minimal, if any, gains from lowering the engagement point. It depends on the setup and what the car is tuned for. More often than not just slapping a VFAC on the car and lowering the engagement point will net you nothing.

Definately disagree. Every vtec dip problem i've seen is a result from the ECU pulling tons of timing at the engagement point - thats what my car did with the emanage ultimate! Of course a poorly designed manifold and a small exhaust will contribute to the problem, but the data logs speak for themselves. I have never personally seen a dyno showing this dip on an EMS-run car.

who says you NEED a cat? there are ways to compensate for the boost creep while still running without a cat (smaller catback with a test pipe, porting the wastegate, the tune, etc)

i ran a HFC with my greddy kit and i kept boost at a very safe 8psi MAX. the only problem was the car was especially sensitive to atmospheric temperatures so i lost quite a bit of power on hot days - even more so than any other turbo car i'd ever had.

like i said, there are a few ways to manage the creep on this kit. everybody's results seem to be different though, so you may have to spend the time to experiment. if you're just looking for a different sound though, i'd recommend leaving it alone...

 

I generally ignore piggybacks. They cause a bunch of problems of their own. They can sometimes be the best choice though.

My statement about more power sooner with lower VTEC is completely true for supercharger kits and EFFICIENT turbo kits with low pressures at the exhaust valves. This is based on multiple dyno tests with the AEM EMS and a variety of VTEC points. I've done testing and tuning myself to explore this, and it seems that virtually everyone else on here who has shared details of their tuning/maps agrees.

Log manifolds with a cat, small turbine housing, and small exhaust seem to be the worst for VTEC dip. Once you add high flow cats, test pipes, 3" exhausts, and larger turbine housings, things perk up quite a bit. (not the least because all of those also generally increase boost)

BTW- I have had an EMS on my car NA, with a log manifold, and with a tubular manifold. There were significant tuning changes (fuel, timing, and VTEC point) between all of those setups.

Tim

 

I would agree with this. If you slap a VAFC on a turbo or supercharged car and lower VTEC without changing anything else, it will probably make things worse, not better. My comments above all assume that you can actually tune the car and not just modify the VTEC engagement point.

Tim

 

If you look at AEM logs and dyno results, you can see a big dip in power from improper VTEC placement (too high or too low). If you graph the timing as well, the dip will be there even when the timing is steady. It's during the tuning process that you would see the dip. On a finished, properly tuned car, there should be either no dip or a minimal dip.

Tim