20v 4ag....power stops building above 7200 rpm

[Grant]

Hi folks,

I have an ae111 20V 4age with kelford 270 duration cams with 8.9mm cam lift. 

I've been chasing missing power for a while now but I'm finally stuck at this peculiar problem.
Over the course of the year I've had a custom 2.25" exhaust made and with a cut-out pipe to bypass the muffler.  This cut-out made me realize my "free flow" Thrus muffler was more restrictive than I thought.

After mucking about with cam timing, getting proper valve clearance, modifying the tune...I'm finally at the point where I think I've done everything but power still drops off sharply at 7200 rpm.  These cams should build power up to 8000 rpm.  I have even opened up the bowls of the head and de-shrouded the valves which resulted in a noticeable improvement above 5800 rpm.  There is plenty of fuel up to the high rpm, the wide-band show me around .87 AFR.  Max timing is 34 degrees, but I've messed around with it plenty.

I am wondering if some how the ignition system is letting me down.  For a stock appearance, I am using a wasted spark setup from a Daewoo/Opel 16V setup. 



Any suggestions?  I'm trying to figure out what I'm missing.  The stock engine is supposed to make peak power at 7800 rpm...






The engine bay picture is how it looks when I want the car to look stock.  For power, I remove the air box and inside are the velocity stacks.  There is a TRD 4-2-1 header on the car too.  Thanks.

[GintsK]

Cams alone did not make [peak] power. It works in unison with intake and exhaust. For what rpms your exhaust are calculated? Is secondary length of your exhaust are "tuned". Removing velocity stacks in most cases just decrease torque, with no valuable power improvement: shorter don't mean more power, you need: air mass, air velocity, resonance at desired rpms. Short trumpets remove mass and makes resonance [if it persists at desired range] yield low.
Anyway some WOT run log-file and/or dyno chart would be helpful for further discussion. What power/torque you have. And what desired?
For n/a ignition coil should not be a reason.

Gints

[irishtwincam]

What cam timing are you running?

http://club4ag.com/faq_and_tech_pages/4A-GE%20camshaft_story.htm

272/272  <10mmlift
Ex. max lift set at 98° BTDC. 
In. max lift set at 100°

272/272  >=10mm lift
max lift 100/100

Also:
16v 4ag with 272/272 setup here.
http://www.vemssupport.com/forum/index.php/topic,463.0.html
Has spark, fuel, o2 and detailed dyno pics.
May make a useful comparison?

Post your fuel & spark maps and dyno sheets.

[Grant]

I haven't been to the dyno yet because I want to get everything working well before I pay for a final tune.

I also don't no the exact cam timing but I have played around with the exhaust cam timing and intake cam timing quite a bit. 

My problem is pretty sudden.  It pulls pretty well up to 7200 rpm then gets soft.  It also makes a sharp noise at after that RPM....but I've pulled timing at that point and it didn't make a difference in power or sound so I don't think it is detonation.

Nothing about the exhaust is calculated...but I'm using the same exhaust header that allowed other people to build decent power up to redline. 

[rob@vems.co.uk]

You've not got a soft cut rev limiter cutting in there have you?
Or any of the antilag settings triggering?

[Grant]

No, I shouldn't.  I will look over the settings again....but I CAN keep going above 7200 rpm...it just accelerates much slower.  My understanding is those types of controls would not let me go above that rpm?

[Grant]

I will try messing with VVT  switch off point.  VVT in these engines advances the cam 30 crank degrees.  At high rpm this become too much.  I'll try fiddling with it.

[GintsK]

I am not deeply familiar with toyota 20V engines, but this year I've tuned 20V engine installed in Lotus Elise.
It has 36-2 on crank and 3 on cam. Engine was equipped with similar to Vtec system with switchable cam lobes for both camshafts and variable intake cam. Initially we toughed that VVT is on/off type. But in reality it was not so: range was close to 45deg - too wide for on/off type. So I was forced to use VEMS camshaft angle control for first time. And it works perfectly! 1.8 L gives us 200hp. No internal mods. Just exhaust header.

[Grant]

That's not a 20V.  That sounds like the 2zzge engine out of the Lotus Elise and Celica GT-S.  20V has just on/off variable cam timing and no lift control.   2zzge is a 16v.

[uzelac]

1ZZ-FE can be found in Lotus cars also.
They use VVTi (variable timing yes, lift no).

2ZZ-GE as Grant said have VVTL-i (variable timing and lift).

Both ZZ are I4 with 16V head.

AFAIK 4AGE (later versions) was only Toyota engine that came with 20V head.

[Denmark]

You Do need to turn off vvt , only enable from around 1800 to 6500 or so, this was the setting that made the most tq and widest powerband,
It is a on/off on the 20v4age


/Skassa

[Grant]

This ended up being due to a restrictive muffler.  I was using a louvered core glass pack at the time, I learned later those are terrible for flow, switching to a perforated core glass pack pretty much solved all of my performance problems at the time!

Grant