NA Silvertop VVT Switch Points

[Loudtoy]

Just a quesiton out there for all you silver/black top guru's
I have a nearly standard silvertop (shaved head) in my rally car, running a mega squirt ecu which means i don't have any fancy load/throttle pos swithing but instead i have rpm based switch points - which are adjustable down to 1rpm.
So the quesiton is, what is the optimum on off points for vvt in a near standard scenario (wish i knew what compresison has been raised to with the shaved head) based on your experiences or the experiences of others.

If your 1st response to this post is why are you wanting to have an rpm based switch point for you vvt can you please kindly read the above or $&#$% off.
Thanks.

[sergei]

It is crucial to make it off @ ~6800, but turn it on say where you will unlikely to use low throttle (cruising mode), say @ ~4000-4500.

[Loudtoy]

Ok sweet so off at 6800, i had it set a little lower but will bump it up a little, not to worried about a constant cruise speed as i can just put a switch in there to turn it off for touring stages. More looking to get rid of the massive flat spot thats there at 4-4500 rpm, just want to have the ability to pull from 4k if i'm half a gear up up out a corner, not chucking it down one to get it moving then back up again 2 seconds later as it gets to the rev limit.
Wonder if anyone knows the lowest rpm level that a car with a standard computer turns vvt on at??

[sergei]

Ok sweet so off at 6800, i had it set a little lower but will bump it up a little, not to worried about a constant cruise speed as i can just put a switch in there to turn it off for touring stages. More looking to get rid of the massive flat spot thats there at 4-4500 rpm, just want to have the ability to pull from 4k if i'm half a gear up up out a corner, not chucking it down one to get it moving then back up again 2 seconds later as it gets to the rev limit.
Wonder if anyone knows the lowest rpm level that a car with a standard computer turns vvt on at??

lowest RPM is idle
It will turn on at idle near 100% throttle.

[Mr Revhead]

can you get dyno time?
if you can you can do runs with it on, then off. over lapping them will give you a good indication.

yeah stock once the engine is past a certain temp, anything over about 1/4-1/3 throttle will switch it on

[ChaosAD]

Ill be doing some datalogging of a standard silvertop ecu soon and can send you the logs if you want them. I've heard the rpm switch point depends on the tps angle.

[Flannelman]

stock ST is 4400, on off like swich

BT varies from temp and load

est on comp is

.010 tho + .3 from 10.5 = 10.8
.020tho + .5 from 10.5 = 11
.030tho + .8 from 10.5 = 11.3
.040tho + 1 from 10.5 = 11.5

[matt dunn]

stock ST is 4400, on off like swich

I have a feeling that is for pre-facelift only,
and facelift silvertop are more variable than that.

Matt

[Mr Revhead]

my 91 with its stock ecu was variable
was NOT rpm based

[Adamal]

I'd imagine it'd depend on other factors such as load etc.

[Rick]

This is from a Black Top 20v

[Loudtoy]

Ill be doing some datalogging of a standard silvertop ecu soon and can send you the logs if you want them. I've heard the rpm switch point depends on the tps angle.

Yeah that would be mint, just trying to figure out the best settings for it, the hole in the mid range is nearly as bad as a stock computer tune which means that it's awfull in relation to the rest of the torque curve

[sergei]

stock ST is 4400, on off like swich

BT varies from temp and load

est on comp is

.010 tho + .3 from 10.5 = 10.8
.020tho + .5 from 10.5 = 11
.030tho + .8 from 10.5 = 11.3
.040tho + 1 from 10.5 = 11.5

I never encountered a ST that behaves like you describe. I think it is an internet myth that started by mixup with Honda VTEC.
I can safely say all ST switch points are throttle based.

[NILPSI]

Have had a vvt light in both my truenos at one point or another (not something i would normally admit too, i was younger and liked blue lights)

From what i remember both silver and black top switch on TPS signal, I could make the silvertop light come on by just giving it full throttle from idle

As people have already commented, it does NOT work the same way as vtec with a simple on/off rpm point on either silver or blacktop

[johntramp]

It is crucial to make it off @ ~6800, but turn it on say where you will unlikely to use low throttle (cruising mode), say @ ~4000-4500.

Why is this?

[sergei]

Advancing inlet cam also makes it closing off early, which is bad on high rpms. At about 6800 is the crossover, where advantage of greater overlap is diminished by disadvantage of early closing.

[sergei]

BTW you could build a small comparator/frequency to voltage convertor out of $10 that will do what stock computer does in terms of switching VVT.

Here is how it will work:

Voltage to frequency converter will provide linear voltage increase with rpm increase which would compare against voltage off TPS on the comparator side (via Schmidt trigger), which would drive the transistor that drives the VVT solenoid.

You will need a standard op-amp chip (with 4 op-amps), bunch of capacitor, resistors and couple of transistors.

[ChaosAD]

Are you using MS1extra? one of the programmable outputs allows you to base it on two variables, I think its output3. Or just upgrade to ms2.

[Loudtoy]

Yeah ms1 extra. will have to have a look into that. At the moment it's using trigger 1 and i'm pretty sure the 3rd output is the one i'm using for my shiftlight. Wil have to have a look into it a a little play when i have the chance. I have a feeling that the two outputs are fixed, ie 50% throttle at or above 3500rpm = on which is still better than on all the time above 3500rpm which is what it's set at now. Can you remember if it has the ability to turn things off as well. Might set it to on at x% throttle and off above 6800rpm if i can figure it out.

Sergi how would your setup work with 6800rpm off function, i can see how it would work to trigger on as rpm/tps setup but off at 6800?? Would also need to sort out a max rpm trigger that turned it off at 6800 which to me would seem like alot of mucking around to get it sorted right

[neo]

Could always be super dodgy, if you have another output spare, have the extra output trigger a relay that cuts the power to the other side of the relay that the first output opened