20v 4age vvt dyno sheet

[QikStarlie]

Anyone have a dyno sheet with back to back runs, with vvt off, then on?
keen to see one n/a and one turbo.

google wasn't playing the game

cheers

[Bazda]

viewtopic.php?t=46369&highlight=7agte

Check here. Mine with VVT off first graph, and VVT on 2nd graph

[QikStarlie]

cheers barry

hmm as i suspected, isnt alot of advantage over correctly adjusted fixed cam timing. other than the last 500rpm or so. and better idle.

do you know roughly what rpm the runs started and ended at?


above overlayed


Edit: that 2nd graph is with vvt on all the time i take it? not switching back off at 6000rpm? cant quite csi the fine print on the left of the plot



anyone with same deal for na?

[Bazda]

That is a big advantage in having the VVT, Huge, check out the mid range power. So not sure what your on about?

VVT is for low end to mid range, not for top end as it advances the timing in that area.
From 2000rpm to 8000rpm

VVT on from 2000-6000rpm

[QikStarlie]

ah, so the 2nd graph isnt with vvt on throughout the whole run?

2nd graph is final tune with vvt on from 2000rpm till 6000rpm. correct ?

[Bazda]

ah, so the 2nd graph isnt with vvt on throughout the whole run?

2nd graph is final tune with vvt on from 2000rpm till 6000rpm. correct ?

1st graph is with no VVT
2nd graph is VVT on @2K off @6K

Both were tuned correctly.

[QikStarlie]

ok that makes more sense. kinda shows what i want to see now. although would be good to see a run with vvt on right through.

i'm not thinking of ditching vvt btw. i don't own a 20v

[strx7]

vvt will always give you more area under the curve. I cannot workout why anyone would want to ditch vvt. for crazy duration/lift cams which need vvt removed the gain of 5-10% top end power for the sacrifice of significantly more low & midrange power and torque, all real world scenarios other than straightline multi km drag the vvt powered vehicle will win everytime.

[1I1]

Because with crazy cams + no VVT you can still have lots of power for a 20v from 5,500rpm onwards

[strx7]

and that same engine with vvt working could have a table top flat torque curve from 5500rpm to 7000rpm, with the torque climb starting at 3500rpm which will make for a far nicer car to drive in anything other than a lightweight single seater with an crazy close ratio box.

[KinLoud]

Mark - is that graph off Daniels mad bt20v with huge toda cams?
If it is... drove it - boy was it a severe slug down low!
3500rpm to get a slow start off from the lights... passed by everything!
Up high yeah it was pretty damn good but sure would have been better with a bit of mid range torque

[Bazda]

The Toda cams allow for VVT operation, but he wanted to run an adjustable inlet cam gear, meaning loosing the VVT.
Would be been good to put the VVT pulley back on and see how it performs.

So noticeable on my car with VVT on and off.

[1I1]

But aren't Toda cams able to work with VVT up to a certain size then you have to remove it?

Though I do agree VVT should be kept on stock cams

[BZR4AGE]

I wish I still have my car, o well, but I think the max you can keep VVT was 288 in with 9mm lift??? also the reason why i ditch VVT and started building it with crazy cams was because the original VVT pully I had was buggered, so decided to ditch it

[Rookie]

There was a really good graph of a silvertop on rolla club showing exactly what you wanted, but alas it seems to have gone.
It made more power with it off till about 2000 rpm then vvt on over took it then at about 6500 rpm vvt off was on top again.

[Lith]

Sounds very similar to what happens with NVCS on RB25DETs, which is a very similar system. I've tuned one "totally" with VCT on and off to get ensure optimal results either way and when overlayed the difference was really noticeable:


Torque only really fell below where it was with NVCS somewhere decently past 5000rpm from memory - and again, with RB25s a LOT of people don't bother at all with playing with valve timing... when an engine is designed to utilise it, its a huge sacrifice in low down/midrange torque for no gain if you don't use it. Partly due to the common laziness in this area RB25s get a bit of a dud rap in regards to their turbo spooling/torque.

If you have VCT from factory, and you haven't massively changed the breathing/combusion behaviour of the engine from factory then IMHO having adjustable cam gears is definitely not a good replacement. At least with the RB, getting an adjustable exhaust gear and leaving the variable intake cam system can result in awesome power delivery

[1I1]

There was a really good graph of a silvertop on rolla club showing exactly what you wanted, but alas it seems to have gone.
It made more power with it off till about 2000 rpm then vvt on over took it then at about 6500 rpm vvt off was on top again.

Sounds like what VVT is set to normally (unsure on exact revs it cuts in/out)

@ Daniel - yeah it's to do with the lift valve from memory that vvt has to be removed. Wheres ace_sniper when you need him

[QikStarlie]

i see vvt as more of a setup, to allow factory to get a nice idle and gain a touch of top end. you can have all that mid range by advancing the inlet cam, to the same cam timing as "vvt on." but will idle rough. plus lose a small amount of peak and not hang on as long, after peak power.

this is how i was running my 16v 4age with 300deg cams. max inlet advance that the valve to piston clearance would alow. was bugger all peak power loss, and it died fairly quick after peak power. rather than peaking slighly higher (few kw) and hanging on a little longer with the cam retarded. running the inlet cam advanced and gaining alot of midrange. was obviously far far better, than running retarded and loosing all the midrange, for a small window of power gain in the last 500rpm.

so yeh, im mostly interested in seeing how much is gained in the top end by switching vvt back off. basically just looking for more examples, of what ive already found with adjustable cam gears.

[Bazda]

In Summary...
VVT does nothing for top end, its turned off.
VVT does not function at idle, its only activated at X rpm and X throttle position.
VVT is best from 2k-6k.
VVT with cams would be awesome, but you cant run massive big cams.

[strx7]

ideally you want to go with the largest lift & longest duration cams you can and still run VVT, this SHOULD result in broadest torque curve available from your engine.