4age 20v Power dropoff - Dyno sheet attached

[shelldrake]

Hey guys,

Did some dyno tuning today and I gained a bunch of power(7-18kw across the whole range with an increase of 9kw from when it first ran(97.2rwkw initially, left with 106rwkw), but I just can't seem to make power above 810-8200. The tuner thought the valve springs used can cause the kind of dropoff seen here as if it were port shape, intake/exhaust, cams - generally the power would just taper. The injectors are are def not maxxing out either. (However, I am using TODA valve springs)

For reference, the cams are approx 270 degree duration with 9.5mm lift. The head has been ported, extractors are an equal length 4-1 design, intake is running 60mm trumpets with socks.There is a 12mm spacer between the intake manifold and the head(port matched to the head).

I know the images are hard to see but it should give you an indication of what's going on.
The two lines show the first and last run, the green is obviously the last.

-So, what was done today - We ran the car with the vvt off all the time, then on all the time -until 6k it proved beneficial to have the vvt switch active, then off above.
-I advanced/retarded the adjustable ex cam gear 3-4 degrees, both we weaker runs than the original positions.
-We bumped the timing up in the higher rpm band. Above 6.5k it proved benefical to advance timing several degrees. When no more power was made, we backed it off a couple of degrees. (No pinging was heard(noticed )





Anyway, if the valve springs themselves were ok, but the associated retainers were damaged, would the clearances the be zero? Would this show the results I am getting? This would mean full lift is not being achieved yet?

[oldcorollas]

are they real toda springs? nto copies?

get one measured for spring force at given valve lift?

maybe they aren7t actualyl any good for that rpm?

[Sam_Q]

thats a really interesting point, lets say the valves are boucing for a moment would the power drop off look like this? is that the normal result seen on a dyno for this? what do you think corollas?

[oldcorollas]

when valves bounced on the 4K while driving.. it was like hitting a wall

haven't forgotten to raise rev limiter?

[Sam_Q]

oh ok, good to know

not that it is the problem but with these power curves they do seem to drop pretty rapidly

[shelldrake]

Rev limiter was set to 8700. They were purchased from Toda australia and came in a toda box with all paperwork, etc. I can only hope they are the real thing.

[oldcorollas]

hmm, 270 is not a huge cam in the scheme of things..

what length are the extractors? they may be giving a good reflection just below 8000 and then just above, they might have a bad reflection.. same for intake...

you might just be hitting the point of negative reinforcement perhaps?

what duty cycle are the injectors running at?
more importantly, what is the length of the pulsewidth vs the length of the engine cycle?

single shot of fuel per engine cycle? 2 squirts?
8200rpm = 137 revs per second
2 revs = 1 engine cycle = 14.6ms
if your PW at that time is around 13-13.2 then injectors might be too small?

[Celica RA45]

what length are your extractors and what dia .also what length is your inlet from back of valve to ram tube ,
and what is the duration at 50 thou and how much lift on the cam

[Celica RA45]

looking at your dyno sheet your torque is dropping off early and tapers so i would say cams{ not hot enough }and look at your pipes length and dia and also try 45mm black tops eddie ps i have a black top inlet you can try

[shelldrake]

The quads are actually blacktop already, I have a spacer plate between the manifold and head to mate the faces properly (the map channel on the bt manifold is exposed when they fit straight to the st head). Will measure the extractors now...

Will check the map again to determine the PW at the higher rev range.

[ViPeR_NiPPleX]

Need to scan those dyno sheets lol. I wonder if you got gibbed on those valve springs? Could they be standard replacements?

[Celica RA45]

if they came in through adrian from toda australia they would be the real deal

[oldcorollas]

i was just thinking of our WA friend who seemed to get dodgy ones... and some broke

[XR Pilot]

If its easy enough to test, might be worth trying a shorter set of trumpets.