I had my car dyno'd last year with my hondata 4b... long story short the headgasket blew. Since last year, i have shaved 10 thou off of my head (warpage due to hg problems) and went from a 87.75mm to a 88mm pistons (same 9.0:1 cr as before).

The question is, how safe is it for me to boost on the original map that was created for me last year? The reason the hg blew was due to an ignition that was installed AFTER the tune, it is back to stock ignition right now until the new dyno tune next week. The motor has been broken in properly for XXXX miles and I want to boost around 6psi or so to make sure everything is running well and there are no problems under load. I have the distributor in the same position as it was when it was tuned. Since the head has been slightly shaved, it will throw the timing off somewhat. So if i set the timing at stock specs with the shaved head, do you think I will encounter any detonation problems due to ignition timing and the tables programmed into the hondata unit? I can monitor all the tables with my laptop if need be, is there anything specific I should look out for? Unfortunately i do not have a wide band.

Attached is the a/f ratio of the dyno, I am not sure how much leaner i will run since displacement has slightly increased and what not.


Thanks for the help


Modified by GudeH23a at 1:54 AM 9/11/2003

 

the motor will run a bit leaner assuming compression (psi, not ratio) checks out the same as before. I REALLY would not beat on it without setting your ign timing first.

 

Ignition meaning with the timing gun or via hondata? I can lay off the boost no problem, it is better safe then sorry.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by GudeH23a &raquo;</TD></TR><TR><TD CLASS="quote">Ignition meaning with the timing gun or via hondata? I can lay off the boost no problem, it is better safe then sorry.</TD></TR></TABLE>

yes i mean by setting your base ign via distributor. Better safe than a little tick tick tick

 

what about possilbly turning up the idle fuel pressure a few ticks?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by VaporTrail &raquo;</TD></TR><TR><TD CLASS="quote">the motor will run a bit leaner .</TD></TR></TABLE>

Your timing will be different even if you have the distrubutor on the same position because of the milled head so definetely get it tuned again. Better be safe then sorry. Also since you up the displacement, the motor should want more fuel so it will run leaner.

HTH

 

So if i set the timing with my timing light, will the hondata ignition tables get screwed up at all?

 

Was it an ignition misfire that you think caused the HG to blow? The reason I'm asking is that i've never heard of that, ever. I've actually stayed into 25 psi of boost for 10 seconds multiple times with a rich mis-fire because I was pissed. NOw, if the ignition was overly advancing your timing somehow, I could see that. However, if you think its just a misfire causing the HG to blow, well I dunno man.

 

There are lots of reasons a head gasket could fail. If it happend a year after the tune-up, that's probably not one of them......

ANyways, for every 12 thousandths you shave off the head, you'll want to advance the camshafts about 1 degree. When the head sits closer to the block, it causes the belt to tension too much in the wrong direction which retards the cam slighlty..... so first set the cam timing, then verify the igntion timing with a timing light to make sure the timing on the display screen matches the actual timing at the crank.

Then you can take a look at the tune-up. If you play with the tuneup before setting these parameters, your only gonnan chase your tail!

-Good luck

 

you can probably get it running great with just a few dyno pulls... drop the 50 or 60 or whatever it costs you in your area and do it. dont skimp when it comes to tuning.

 

The headgasket blew as soon as the ignition system was installed. The reason it blew was because the timing was overly advanced. I made a few threads asking if it was ok to install it after the tune and asked the tuner as well as several other people if it was ok to install, well i found out it wasnt.

I am not skimping out on the tuning, i have a dyno appt next friday the 19th. Thank you for all of your replies, I know I can always get the best help available on this board