i posted something like this b4 but this dyno now has the air/fuel ratio displayed now.
the vtec point is set at 5400. i could only get ahold of the final dyno graph.

i ran on a Dynojet 424X - which can do front wheel, back wheel, and 4 wheel drive cars

3rd gear run tuned with a vafcII.
mods: check sign

i was expecting more whp, could this just be a bad tune job?

 

i persoanlly would say its possibly a little too lean, and the fact that the vafc cannot alter timing. a chipped ecu tuned for that setup using Crome should make better power.

 

yea i'd say its a little lean. But thats pretty good a/f line for cam tuning with afc.

 

Yea those numbers are low. Could just be the dyno tho. What other supporting mods do you have?

 

get a real tune with crome or hondata.

 

i agree looks a little lean and try a 4th gear dyno run.

 

it looks like the fuel cutt off or rev limiter made my revs stop around 7400. i have the upgraded vavletrain and i heard i can rev to 7800 which i thought was the stock limiter. so why am i getting cut off so early?

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 94Vtecluder &raquo;</TD></TR><TR><TD CLASS="quote">Yea those numbers are low. Could just be the dyno tho. What other supporting mods do you have?</TD></TR></TABLE>

i heard that this dyno the new dynojet 424x reads a little low. i have a megan header, an ebay intake, and a catback exhaust 2.5" piping.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by DOHCVTEC190 &raquo;</TD></TR><TR><TD CLASS="quote">i agree looks a little lean and try a 4th gear dyno run.</TD></TR></TABLE>
how much hp can be gained from a 4th gear run, i heard when tuning u can be in 3rd or 4th.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by v4lu3s &raquo;</TD></TR><TR><TD CLASS="quote">i persoanlly would say its possibly a little too lean, and the fact that the vafc cannot alter timing. a chipped ecu tuned for that setup using Crome should make better power.</TD></TR></TABLE>
is it dangerously lean, the tuner said he tuned the same setup on another lude with the same results. he altered timing at the distributer, even though i have skunk cam gears on.

thanks to all for the feedback by the way.

 

no its not dangerously lean at all. Typically the H22's target a/f's run from 13.1 - 13.7

at a couple points, you are just over 14.0. Its not that lean, but you could use some more fuel.

 

what about the fuel-cutt-off or the rev limiter, do u know what's going on there?

i heard it should be at 7800, but i can't get past 7400....i am throwing a knock sensor code but i doubt that's it.

any ideas would be appreciated , thanks

 

thats prolly why you arent making any power. Knock sensor codes retard the timing and dump fuel to keep the motor from detonating. Personally im suprised that you are even able to rev to 7400.

 

almost 14:1, thats gotta be dangerous.

 

thats not dangerous at all.

16.1 is getting there and anything above it is heading towards dangerous grounds.

 

interesting. When i race i rev the engin to 8g's i dont know how accurate the stock gauge is though. Were you on it all the way up to 7500 or did you back off?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by nismo350z &raquo;</TD></TR><TR><TD CLASS="quote">interesting. When i race i rev the engin to 8g's i dont know how accurate the stock gauge is though. Were you on it all the way up to 7500 or did you back off?</TD></TR></TABLE>

i held it until the rev limiter kicked in.

i am throwing a 23 CEL - knock sensor. i thought it didn't hurt performance but i searched alot and found out that when u throw a 23 CEL ur ecu runs with basic timing(or something like that) in order not to cause a knock. when ur knock sensor is running fine ur ecu advanced the timing in ur car until it detects a knock thus gaining more hp. so if it cannot detect knock it goes with a basic setting which can be what is hurting me.

so i wonder if this will also fix my early rev limiter problem.

i now have a new used knock sensor and will be installing it within the next few days, so we'll see what happens.

 

i dont think you understand what knock is.

when the sensor detects knock, it retards the timing to "cool" or lower the cylinder pressures, essentially.

what i dont understand about urs is that when i used to have a knock sensor, the ecu wouldnt let me rev beyond 6800. Alot of people confuse the 6800 rpm rev limiter with limp mode, which is really very different.

remember, if your motor is knocking, that is not a good thing.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 98vtec &raquo;</TD></TR><TR><TD CLASS="quote">i dont think you understand what knock is.
when the sensor detects knock, it retards the timing to "cool" or lower the cylinder pressures, essentially.
</TD></TR></TABLE>

i may not understand fully but from what i gather u are right. but if u have a broken knock sensor ur engine runs at baseline timing because this way idealy no knocking can occur.

once fixed and running right ur ecu advances the timming until it detects knock and then retards the timing to deal with the knocking.

i am really hopping about the limp mode to, although i also would think that 6800 would be the rev limit in this case, not 7400

thanks, i hope to replace today and find out.

 

ok one thing. i don't do dyno tuning but i would like to know about which gear to be in.

i always thought you had to be in the gear with the ratio closest to 1. which in preludes is 4th gear. if you use any other gear it will give an inflated/deflated number

corret/incorrect?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by oranginal &raquo;</TD></TR><TR><TD CLASS="quote">i may not understand fully but from what i gather u are right. but if u have a broken knock sensor ur engine runs at baseline timing because this way idealy no knocking can occur.

once fixed and running right ur ecu advances the timming until it detects knock and then retards the timing to deal with the knocking.

i am really hopping about the limp mode to, although i also would think that 6800 would be the rev limit in this case, not 7400

thanks, i hope to replace today and find out. </TD></TR></TABLE>

the knock sensor won't detect knock at all with a healthy engine. Its simple man. You have a set timing for when the computer doesnt throw any codes. When it detects knock or the sensor is broken, the computer retards the timing approximately 3 degrees (so i have read). Once the sensor no longer detects knock or you replace the broken sensor, it goes back to the original timing values.

your tach could be off, but i know for a fact that when you have a knock sensor code, the rev limit is dropped to 6800 rpms.

limp mode is the computers safety backup fuel and timing map. In limp mode, it doesnt read off the factory map at all. In limp mode, you have a rev limit of 3000 rpms. Once you have been in limp mode, you will know the difference.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by oranginal &raquo;</TD></TR><TR><TD CLASS="quote">[b]


i have a megan header, an ebay intake, and a catback exhaust 2.5" piping.


</TD></TR></TABLE>

bing bing bing. That megan header while alone isn't the only cause of your crappy numbers it definitely does not flow near enough to maximize the potential your engine has. If your serious about this build get a SMSP or hytech or AnR. Hell if your low on cash a moddified greddy would out perform that megan.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 94Vtecluder &raquo;</TD></TR><TR><TD CLASS="quote"> If your serious about this build get a SMSP or hytech or AnR. Hell if your low on cash a moddified greddy would out perform that megan.</TD></TR></TABLE>

i am thinking of just doing the 2.5" collector mod on the megan header. <TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 98vtec &raquo;</TD></TR><TR><TD CLASS="quote">You have a set timing for when the computer doesnt throw any codes. When it detects knock or the sensor is broken, the computer retards the timing approximately 3 degrees (so i have read). Once the sensor no longer detects knock or you replace the broken sensor, it goes back to the original timing values.

your tach could be off, but i know for a fact that when you have a knock sensor code, the rev limit is dropped to 6800 rpms.
</TD></TR></TABLE>

couldn't of said it better myself. but i also have a vafc and an rsm from apexi, both read around 7400. i know i am def getting past 6800 which i thought it should stop at too. i just hope replacing this thing fixes all this and i can rev normal again.

thanks to all once again for the feedback

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by oranginal &raquo;</TD></TR><TR><TD CLASS="quote">i am thinking of just doing the 2.5" collector mod on the megan header.

couldn't of said it better myself. but i also have a vafc and an rsm from apexi, both read around 7400. i know i am def getting past 6800 which i thought it should stop at too. i just hope replacing this thing fixes all this and i can rev normal again.

thanks to all once again for the feedback </TD></TR></TABLE>

Okay that should help but it still isn't near the potential. AFAIK the primaries on the megan are smaller than the greddy which are even smaller than smsp, hytech, anr etc. etc. Plus the design isn't all that good in general.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 98vtec &raquo;</TD></TR><TR><TD CLASS="quote">thats not dangerous at all.

16.1 is getting there and anything above it is heading towards dangerous grounds.</TD></TR></TABLE>

First of all, it IS dangerously lean. Do you tune or what? I sure hope not..

My prelude detonates all over the place above 16.1 at PARTIAL throttle..

Peak torque, and therefore HP, in theory, is around 13.1 to 13.2 AFR.. tune for that..

You need to tune for inconsitencies anyways, don't tune on the edge thats asking for it..

regardless, 14:1 is WAY too lean for full throttle.

 

um, yea. I do happen to tune my own car. at part throttle, i tune my car to 15.1

no problems whatsoever. If you are detonating at that a/f, you have an ignition problem.

14.7:1 is a perfect mixture and if you are detonating at an a/f richer than that, you have problems.

go ask any other tuner and see what he says about 14.1 at WOT. It is NOT dangerously lean at all. For a boosted motor, yea its pretty lean for WOT.

refer to this graph.


thats the way its supposed to be done, generally. So as i said before, 14.1 is not dangerously lean at all for NA or stock motors. Boosted...yea, its lean. But thats not the case now is it?


i tuned my car to ~13.5 at WOT.

find me someone with credibility that says 14.1 is dangerous at WOT on a non boosted, non race car and i will shut up.

 

Determining what proper air fuel ratio to run really depends on several things such as compression ratio, fuel oct, etc.

14.0:1 a/f ratio at wot with the posted setup would not cause detonation nor engine damage, but I would not recommend it due to the fact that it is on the leaner side.

I would suggest running .3-.5 a/f ratio richer (13.0-13.7:1) range with the setup posted.

1. I recommend you perform a leakdown/compression test
2. I recommend you find a crome, hondata, uberdata tuner etc.
3. Sell the vafc, buy a chipped ecu.
4. Dyno tune the car

 

Since the a/f graph is a little under 14:1 the whole way, I don't think it's anywhere near dangerous. You won't find a whole lot more horsepower by tuning the a/f either judging by where it is now. Check your ignition timing, and you may find it should be adjusted a bit. After my crower stage ones on my h23 and before the tune, I had an a/f of between 15:1 and 16:1 and at some points it was slightly above 16:1. I had absolutely no detonation or known damage to the motor, but just whiteness on the spark plugs. No biggy if it's below 14:1