Power peaking early?

**Stav** · 01-06-2006, 12:37 AM

Well I have kept quiet as far as power mods go lately but I need some suggestions...
My cars power is peaking at 4800 rpm on 2 dynos and the gtech. I am certain something is holding it back .I do know it is running lean up top and hence there are a few more killowatts to be had.However even before this current tune it was the same old story...my power was peaking at 4800rpm..way too early. I have retarded the cam more than I care to remember..Could it be valves springs ? Could it be simply running out of fuel whilst the tune is too lean and pinging? The compression is good. Any suggestions are welcomed.

FS5 · 01-06-2006, 07:57 AM

what headers are you running on yours again ,i can't rember.
ive seen a lot of jmm cars peak around the 4900 rpm mark .with my old head and the streetfighter cam it peaked at 5300 rpm this is with lukey headers .maybe some bigger pipes will help.
did retarding the cam increase your power curve much ?

**Stav** · 01-06-2006, 10:15 AM

Quote:

Originally Posted by FS5

what headers are you running on yours again ,i can't rember.
ive seen a lot of jmm cars peak around the 4900 rpm mark .with my old head and the streetfighter cam it peaked at 5300 rpm this is with lukey headers .maybe some bigger pipes will help.
did retarding the cam increase your power curve much ?

I am running the jmm headers. Retarding the cam made no difference to the power curve. The car still peaks at the same rpm. Is it really bad to peak at those revs? I would have thought that peaking a bit higher should see more power ?

FS5 · 01-06-2006, 03:18 PM

well the headers should be up to the task
interesting that retarding the cam made no difference .in mine when i retard or advance it it makes heaps of difference to what rpm peak power is.
you would think more rpm = more power .
after i fitted my ported head ,the streetfighter cam peaked @4900 rpm whereas it peaked @ 5300 before,maybe the head is restricting it .you'l have to bolt your new one on and see.
i have found that the best qter times i have achieved is with the power peaking around the 5300 mark.running with the standard rpm limmit.

HLC · 01-06-2006, 11:55 PM

on a side note, Stav, check the sidewall of your left rear tire... you had a bit of rubbage on the gutter leaving titans ;)

GK · 02-06-2006, 12:56 AM

Quote:

Originally Posted by HLC

on a side note, Stav, check the sidewall of your left rear tire... you had a bit of rubbage on the gutter leaving titans ;)

A side note for a side wall! LOL!

GK

**Mechan1k** · 02-06-2006, 09:05 PM

Maybe try a different cam ... but then there's a cost in it though.
Noticed with Joe's cam it depends on the dialling in of it that makes a huge difference ... noticed it on Regie's car when it was setup for auto .. and when he changed the to a manual .... had the cam dailled back in for the manual ... damn it made a difference ... so instead of peaking early .. it makes power from mid range all the way to redline now (whereas auto it was making bottom-end to mid-range power).

I had a chat to Joe about a cam today ... it maybe in the pipeline ... but i will be setting mine up for bottom-end-mid range power .. especally me being auto ... and EGAS engine ake NO top end power whatsoever due to throttle body restrictions due to mixer ring ... i just want bottom end torque ... hence mine will be tuned that way.

FS5 · 03-06-2006, 09:03 AM

just another thought mate,after reading a thread on how inaccurate the au tach is .could your tacho be out?

**Stav** · 03-06-2006, 09:06 AM

The rpm reading actually came off 3 different dynos and gtech

mik · 03-06-2006, 07:47 PM

Quote:

Originally Posted by useless

Well I have kept quiet as far as power mods go lately but I need some suggestions...
My cars power is peaking at 4800 rpm on 2 dynos and the gtech. I am certain something is holding it back .I do know it is running lean up top and hence there are a few more killowatts to be had.However even before this current tune it was the same old story...my power was peaking at 4800rpm..way too early. I have retarded the cam more than I care to remember..Could it be valves springs ? Could it be simply running out of fuel whilst the tune is too lean and pinging? The compression is good. Any suggestions are welcomed.

i don`t know what the go is with your engine but i thought you might be interested, this hi flow cat i think its better than the type that guys are commonly getting here is the link..... http://www.importbitz.com.au/exhaust.htm i think this is a much better cat i bought a hiflo cat for myself and seeing a metal cat internals compared to another major brand name the metalcat looks much better

**Stav** · 04-06-2006, 12:23 AM

Thanks for that!! But I already have one of those babies.

**Stav** · 17-06-2006, 10:02 AM

Well it continues on.. 140 kmph and the car dies in the butt!! Maybe the ba intake pipe is restricting me? This same phenomena happened to me at wsid on my run and I was hitting 4800rpm and 140 kmph then no more power .This happened before the dam line!! If only I could sort this problem out!! is there any way of testing the broad band manifold changeover point or if it is working at all ?

BTW only 1 dyno showed my power dying at those kmph and that is Joes at crescent motorsport.It depicted what was happening on the track.Dyno dynamic all show me getting past 140 without dramas.However rpm peak was correct on all dynos.

**Mechan1k** · 17-06-2006, 11:15 PM

It's OK Stav ... I get to 60km/h ... and I have no power at all ...actually ... it's more like 40km/h for me.

Take it back to Joes and have a chat with him ... he might be able to diagnose the problem with a little dyno time ... but i guess you have gone through that a few times though.