[Blue01Street]

Got a Dyno done and my torque takes a dive after 5000 RPM. When I plot against my A/F ratio for that run this is what I get. Is that what's killing my torque? This is run number 10, after adjusting my cam gears.

I'm running Crower Stage II cams and a Kamikaze Race Header. I thought that combo should make torque at higher RPMs.

I am getting a re-burn on my chip to lean it out some, and I'll get another Dyno after that. But, I'm just wondering what else might be adjusted in the chip? It's 300 miles one way to a Dyno and I'm just trying to save a few trips.

By the way this is an automatic, so 124 lb of torque isn't terrible.

Sorry about the picture size before. I thought everyone had a 20" LCD monitor running 1280 X 1024. It didn't look very big here.

[ 12-18-2002, 09:28 AM: Message edited by: Blue01Street ]

 

[Travis]

You would see substantially better gains in torque EVERYWHERE except over 7000 grand with a 4:1 header from fs or the 4:2:1 header from fc. The 10 inch primaries as i said before do not start picking up and putting down the torque until AFTER 7000 rpms on the fs or fc headers. beyond 7000 your resonance tunning with those short primaries will put you up over.. however your af doesn look rich but its not worth all htat much as long as you dont start detonating. If you look at your graph before your peak you have the same substantial decrese in a/f # with a massive torque dive. dont believe tunning for a constant a/f would release any more then 5-7 foot lbs even in the worst cases on sucha small engine

 

[Blue01Street]

What if the timing is too far advanced? Would that cause the torque drop?

 

[Travis]

Timing SHOULD only make more unless your detoing.. The real way to play with timing is to bump it and bump it until your power declines and then set it back 2 or 3 degrees from where power starts droping to be safe. That should give you optimal timing.. Im thinking depending on how you have your cams set that your compression ratio is hurting you quite substantioally though... Dynamic compression ratio will be in the 6.9 to 7.2 range... not horrible... but a static with 10.5 or 11 would REALLY help that high end torque production as well as a good low end increase.. Im not sure exactly what cr you would need to run to get your dynamic to 8 but some research in that area would grab you much more gains then the chip could... and it would be cheap too. only about a 100 dollars to mill a head and replace the head gasket. and if you do get your head milled your timing will probably all change.. im guessing your running some pretty big timing with that dynamic being as low as it would be with just a straight cam change.

 

[Travis]

ok i did the work for ya... with the intake cam centerline set 114 degrees atdc and the exhaust cam set at 124 degrees btdc you need a compression ratio increase of about 10.5 :1 for every degree you retard the intake cam you will loose approxiamtly .06 of a compression point.. and for every tenth of a static compression point you gain .08 of a dynamic compression point. This calculation ONLY works with these cams and these are fast sketchy equations i urge you strongly to get a pro to figure this stuff out for you just in case this is wrong. <dont wanna be responsible for an engine. remember your timing will need to be retarded substantially from what it is now because of the big number increase in dynamic. BTW right now your running a 7.26 dynamic compression ratio. most of the gains you feel will be after 3500 rpms and is a non changing increase of approxiamtly 5 to 6 percent all the way across.. so your graph shouldnt flatten up top but should raise everything up. I think your car would really like an intake manifold at this point. shorter runners helping those higher spinning cams with inertial tunning would be a match made in heaven

 

[tdot-zx3]

Thats wierd.. And this is sorta of offtopic.. sorry..

But we dont see enough AutoDyno sheets.. When i had all my mods on my car.. It felt the same way.. Fell flat in the upper RPM.. I never had it dynoed though to see, ill wait till spring.. The dyno sheets ive seen.. curves dont seem to look like the ones from a manual at all.

But Im wondering is this may be a common Auto thing?

 

[Blue01Street]

?

 

[tdot-zx3]

Uhm.. err..

Ya dont worry..
Forget i posted.

 

[Blue01Street]

Originally posted by tdot-zx3:
Uhm.. err..

Ya dont worry..
Forget i posted.

<font size="2" face="Verdana, Arial">I wasn't questioning your post. Sorry if it looked like that. I just wanted to post my Signature to show my mods and I needed at least 1 character in the message field. I guess I should have picked a different one.

Travis went through this big thing about getting my head milled to raise my compression. Like low compression was the cause of my problem. I just wanted to show that I already had my head milled .040".

And why point out that other choices for a header would have been better? Just to say I made a mistake when I bought my header? OK, so maybe I made a mistake. But, I've already got that one. I just want to make the best of what I have not the best in the World.

If the Kamikaze "do not start picking up and putting down the torque until AFTER 7000 rpms", why does my torque peak at 5000 RPM? You would think that if what Travis said is true that the torque would be INCREASING at the higher RPMs.

Does a torque curve rise, fall, then rise again?

You can't really count that little loop at the start of the graph. When the plot was taken he was at a steady 2000 RPM at part throttle and the A/F ratio was about 15:1. He went WOT to start the run and that's where the A/F ratio drops and so does the torque.

Thanks for the tips on cam timing. I really appreciate that "you did the work for me".

[sarcasm]I guess the 8 runs that I made tuning the cams for best torque were just a waste of my time.[/sarcasm]

I really don't care that the Kamikaze header makes best torque AFTER 7000 RPM. I just want to know how to tune for the best torque curve I can get in MY operating range.

I really do appreciate any an all replies. But, I'm looking for suggestions on how to make the best of WHAT I HAVE. Not a shopping list.

[ 12-18-2002, 09:40 AM: Message edited by: Blue01Street ]

 

[Blue01Street]

Originally posted by tdot-zx3:
But Im wondering is this may be a common Auto thing?

<font size="2" face="Verdana, Arial">Any others with automatics seen the same thing on your Dyno run?

 

[dcoFocus]

This might be an auto thing. I have a bone stock auto, and I can really feel power dropping after about 5500RPM, it just feels like its struggling to breath at that point..sorry I'm not much help.

- dcoFocus

 

[Travis]

Actaully when i was talking about timing earlier i was talking about ignition timing. and im sorry i wasted 15 mins of my life going otu of my way to help you. It wont happen again.

 

[Blue01Street]

Originally posted by Travis:
ok i did the work for ya... with the intake cam centerline set 114 degrees atdc and the exhaust cam set at 124 degrees btdc you need a compression ratio increase of about 10.5 :1 for every degree you retard the intake cam you will loose approxiamtly .06 of a compression point......

<font size="2" face="Verdana, Arial">Not trying to argue, but this is the cam timing that i was refering to.

 

[Blue01Street]

Originally posted by Travis:
im sorry i wasted 15 mins of my life going otu of my way to help you. It wont happen again.

<font size="2" face="Verdana, Arial">I'm sorry you feel that way. Like I said, I appreciate any and ALL replies to my post. It's just that in my FIRST post of this thread I mentioned that I had tuned my cam gears during the Dyno runs. I thought that that was the BEST way to tune them. Theory and degree wheels are great as a starting point, but actual performance is the tale of the tape.

 

[Travis]

I was refering to a basis so that you could determine what your dynamic compression ratio was and shave your head accordingly thats why i told you for every degree off of that how much dynamic you lost. But since you already had this process done it wasnt nessasary.