Why can't I make power above 7500?

[shelldrake]

Hey guys,

Just wondering if you have any thoughts/input.

The problem:
On a recent power run this setup made around the 100rwkw mark at 7500rpm... But doesnt seem to want to make anymore above that. The cams are obviously more agressive than the standard cams, surely this would raise the power band (?) My current thoughts include the inlet manifold overall length, Fuel pressure regulator too limiting, fuel pump supply inadequate or perhaps the injectors cannot meet the demand. How can one tell if the injectors are not able to support a particular application? (Or power) Surely power is proportional to fuel consumption.... Is it better to overdrive a smaller injector or underdrive a larger one... It must also be related to maximum airflow though too right?

Not sure what other information may be really relevant, but anyway -

the recently rebuilt 20v has the following specs:

Race ported head, match ported manifold, blacktop qauds (12mm spacer plate between head and manifold)
60mm trumpets and socks.
Approx. 270 degree cams, 9.7mm lift (.382")
TRD .8 mm h/g, approx 11.1 compression
Standard s/t pistons with chrome top rings
ACL bearings, Standard s/t rods with ARP bolts
Extreme light f/wheel
4-1 race extractors, 2.25" exhaust
Standard s/t injectors

Fuel system - surge tank, Bosch high pressure pump, facet lift pump, standard fuel pressure regulator on rail.

Thanks in advance...

[RobertoX]

What computer are you running?

[70XIN]

Any tuner should be able to tell you what duty cycle your injectors are running at any given time, therefore working out whether they are "too big" or you're dangerously close to leaning out

BUT from the looks of your post, you might not be running aftermarket management at all....?


Your power is definitely down a few KW from what i expected .. i would've thought somewhere around ~115rwkw, give or take 5, so somethings going on

edit: removed one comment, i didn't read properly

[70XIN]

And also, power is not completely proportional to fuel consumption

Adjusting ignition timing to suit your setup will also play a very big role

This is (if you're running a stock computer/SAFC) where the lost power is no doubt stemming from, and where aftermarket management will win

[rthy]

standard injectors should be good for heaps more than that

[ke70dave]

<div class='quotetop'>QUOTE (Sam_Q @ Jun 19 2008, 11:23 PM) <{POST_SNAPBACK}> (index.php?act=findpost&pid=549147)</div>
standard injectors should be good for heaps more than that[/b]

yeah that my thinking too...

do you have a dyno read-out of your 100kw@7500? what is a "power run"?

be nice to see the Air/fuel ratio as it approaches the 7500 and beyond.

as the others have said, do you have a programmable ecu?

[70XIN]

<div class='quotetop'>QUOTE (ke70dave @ Jun 19 2008, 11:28 PM) <{POST_SNAPBACK}> (index.php?act=findpost&pid=549149)</div>
yeah that my thinking too...

do you have a dyno read-out of your 100kw@7500? what is a "power run"?[/b]

a run without tuning, just strap it down and run it to rev-limiter

you get your power figure

yay

[SpotterOne]

Mine is kinda similar to that only 16v instead of 20v, and it is still pulling hard with no sign of letting up when it hits the revlimiter at 8k.

As someone said before, what A/F is it running at full throttle/big revs, and what duty cycle are the injectors at?

Have you set the injector pulse properly? At 8000RPM it should be 0.015s.

I tuned a WRX once that had a similar issue, and found that it was out of injector duty. Your standard ST injectors should still be ok with that sort of setup, as mine run at 65%. I am, however just about to change to a set of 4AGZE injectors just to give me a little more headroom.

[Oly AE86]

My ST is stock engine just with programmable ecu and runs 92kW ATW. With your cams and higher CR you should be making more than 100kW, 115 at least. I think injectors would be able to support upto 120rwkW, but as said tuner would be able to tell you the duty cycle.

[rthy]

I think theres some pretty big assumptions about power figures on here. I have seen 75 to 125rwkw for the same engine setup before that I believe were two engines making simular power. I know dynos are only meant to have a 10% varience but from what I have seen its total crap. Dyno power figures are good for comparasins on the same dyno only, and only then its assuming the tempreture and humidity hasnt changed between dyno runs.

[Gunner]

^^^ thats correct sam, between the different bands and types of dyno, there can as muxh as 100hp difference, and then with dyno's like dyno dynamics, you have shootout modes, that can sometimes almost double the actual figure(its a wank fest kinda thing)

I'd like to see the dyno sheet, whoever did the power run should of told you what was going on. If they didnt thats a pretty piss poor effort, even on dyno days, ill tell a customer whats wrong with their car.

but post the sheet and that'll give us an idea whats going on.

Rhys

[Gunner]

Have you done valve springs mate?

[slydar]

yeah you need to give more specs re ecu. alot of ecu's tell injector duty cycle so thats easy to work out. though there are theoretical power limits you can calculate for injectors based on flow/pressure.

could also be cam lob centres.. even a cam a tooth out.

what brand are the cams? maybe speak to the manufacturer/supplier and see what theyre meant to be set at.

bigger injectors if thats whats needed are pretty easy for a 20v. stock 1j or 3sgt.

i dunno about the 115kw atw's though, maybe if youre lucky, most stock 20vs make about 90 atw's.. 25s a big jump. possible i guess, there are alot of variables.

if youre tuner isnt familiar with 4ag's tell him to run alot of advance.. around 40* or so.. at the track youll need a decent radiator to keep up with that though. the short rod ratio (no, i do not meant bore/stroke ratio) means the piston doesnt dwell at TDC for very long, making 4ags very knock resistant, so you NEED to run this sort of advance to make good power.

also is the engine run in? itll make more and more kws as it free's up.

[SNAP]

<div class='quotetop'>QUOTE (Sam_Q @ Jun 20 2008, 06:51 AM) <{POST_SNAPBACK}> (index.php?act=findpost&pid=549228)</div>
I think theres some pretty big assumptions about power figures on here. I have seen 75 to 125rwkw for the same engine setup before that I believe were two engines making simular power. I know dynos are only meant to have a 10% varience but from what I have seen its total crap. Dyno power figures are good for comparasins on the same dyno only, and only then its assuming the tempreture and humidity hasnt changed between dyno runs.[/b]


Id pay that, it also depends on where abouts the tuner places the dyno sensors, i had my once SR tuned and it got 241kw, i tell u it didnt feel like 241 kw it a dato.. then got the shits took it to a recommended tuner.. which was Unigroup at girraween, and found some issues, tuned it again and got 205kw and that felt and drove like it was 205... he pointed out to me all the numbers at the verry bottom of the dyno print out its a list of all the parameters the dyno is reading.. it kinda looks like code, anyway he pointed out to me that it had been botched and is very easy to do. i believe him because with a lower pwr output it felt like it had so much more power top end, had more torque came on boost earlier... be very very wary of tuners, Testimonies r good, and gold figures arnt always that gold

[shelldrake]

The ecu is a wolf 3d version 4. Has had the latest firmware updates performed.

Regarding cam timing, -

(Inlet cam is advanced one tooth)
Inlet opens at 33 BTDC and closes at 64 ABDC

Interesting remark regarding timing - It doesnt seem to ramp up much with vvt on... (26 at 4000 steps up gradually to the 29.5 at 6000, then flat all the way to 8500)
Ignition timing - from 6000-8500 timing its' max at 29.5 at full rpm/load

Map setup using tps.

I don't know where the pulse is set actually, but the fuel seems to be at about 8 at 7500 then drop to about 7.46 by 8500 (At 107 % load)

Dyno chart is as follows -

dyno sheet: After 1000kms. (Has done about 2500 now, and still has some blowby! But thats another story)

http://my1.photodump.com/Anonymous/20v-T.jpg (http://www.photodump.com/Anonymous/20v.html)

[shelldrake]

I should also add, it is running sequential injection with 1zz coil on plugs...

[SpotterOne]

Inlet cam advanced by 1 tooth? Thats 20 degrees!!!

That dyno curve looks like a restriction somewhere - perhaps in the exhaust or maybe your inlet runners are the wrong length.

[blair]

think of the positives!

you still have more power than a 4ac revving its tits off

@ 2.5k!

[shelldrake]

I'm trying to push the limits here... My comparison is a 97rwkw 3t/2tg hybrid which I previously had...

Thanks for you input though.

[shelldrake]

Rang clive cams where the grind was done....Said it should make more power....

[slydar]

more timing advance for sure. some people who run fixed timing with carb sets ups run over 30*.

but like, with the blow by issue, are you sure the bottom end is right?

[shelldrake]

<div class='quotetop'>QUOTE (slydar @ Jun 20 2008, 05:19 PM) <{POST_SNAPBACK}> (index.php?act=findpost&pid=549477)</div>
more timing advance for sure. some people who run fixed timing with carb sets ups run over 30*.

but like, with the blow by issue, are you sure the bottom end is right?[/b]

It doesn't sound noisy or blow smoke. I havent done a compression test yet though... I just put it down to the chrome rings... The cooling setup makes my motor run quite cool - around the 70 -80 degree mark when cruising. 90 in stop start traffic.

[slydar]

if anything there'd be more power in that (cooling). but still doesnt explain the 7500 rpm ceiling.

so you mean blow by as in what though? oil.. somewhere?

[shelldrake]

<div class='quotetop'>QUOTE (slydar @ Jun 21 2008, 12:48 AM) <{POST_SNAPBACK}> (index.php?act=findpost&pid=549692)</div>
if anything there'd be more power in that (cooling). but still doesnt explain the 7500 rpm ceiling.

so you mean blow by as in what though? oil.. somewhere?[/b]

I have the two outlets from the cam cover going to a catch can with a filter on top. A visible oil vapour vents from the filter. This can has started to fill up a little bit. I meant that by running at the lower temperature (and also taking a little time to warm up) does not allow the rings to expand at the same rate.

I think I will take it to another tuner soon and also try some different trumpet lengths and ramp the timing up a bit more. If these motors are as ping resistant as you guys say, it seems like a good thing to try...

[Gunner]

id like to see your afr, and timing maps. But i do strongly suggest seeing another tuner, and also I'd check your exhaust aswell, maybe your cat can't flow enough.

the only thing i can really think of why its laying over so early is restriction which has been mentioned, or your tuner doesnt have a clue, you can make that power opening up a std blacktop, let it rev with a good exhaust, and intake, itll make close to that power.

[shelldrake]

<div class='quotetop'>QUOTE (gunbz-r @ Jun 21 2008, 10:44 AM) <{POST_SNAPBACK}> (index.php?act=findpost&pid=549787)</div>
id like to see your afr, and timing maps. But i do strongly suggest seeing another tuner, and also I'd check your exhaust aswell, maybe your cat can't flow enough.

the only thing i can really think of why its laying over so early is restriction which has been mentioned, or your tuner doesnt have a clue, you can make that power opening up a std blacktop, let it rev with a good exhaust, and intake, itll make close to that power.[/b]

The exhaust should be adequate... 4-1's(tuned length), 2.25", one offset (but free flow muffler), and a second straight through muffler on the back....

-Thanks for your input. Will post how I go in a few weeks....