Hey all,

I had a good time tonight helping a friend of mine tune his ITR.

Here is his setup:

10.6:1 compression
Skunk2 stage 1 cams, finally lashed to spec .0065"/.008"
Titan cam gears (+10/-10 setup at teeth easy to read)
3" AEM intake cold air w/ header wrap
ITR JDM DC 4-1 header/2.5" carsound cat w/stock 01 ITR cat back
Laitner and Bush prepped 64mm TB
Stock Ignition system with (I believe a 7 heat range copper NGK)
Endyn breather kit
Mobil 1 5w-30
Comptech 6lber
Exedy Organic clutch
4.785 final with stock USDM ITR Tranny

Here is what I found interesting. We began picking up gains along the
rev band when we retarded the cams... strange?! I like learning by doing,
and seeing how these cams reacted to adjustments interested me. Usually ITR/CTR cams like to be advanced... these are bigger, however I figured with
more overlap it would want the intake valve closed earlier!@#$&? Weird.
WHen tuning we kept the VTEC at 5700 for the first 5 runs, which is what it
took for us to determine what cam settings would be ideal. Not knowing the
limits to these cam angles, I said hmm... Im not advancing or retarding past 3 degrees at the tooth... so there was my range.

Our goal was to fatten the midrange up as he likes to road race and wanted
to be able to roll out of a gear from 5K-7 and up. With the VTEC stock, he
flirted with the engagement point alot and tended to break traction a bit,
so we were interested in finding a good global increase. When tuning cams
it seems like now it would have been a good step to lower the VTEC to say 4000
and make the runs tuning the cams where VTEC would be the most linear in
the midrange. At that point, raising it to 4500-5K would have made a good increase.

Where we were at before, the cam installer had lashed the valves from the
valve stems instead of the cam lobes. This made for some interesting results
when he posted gains on the dyno before, we are talking 123/123 at 5252...
with a 4800 VTEC point... pretty sick on a almost Stock ITR. Funny, though
we couldnt duplicate this power from 4800-5750rpm. Remembering that there
was absolutely NO valve lash last time surely explained it... not to mention the
nearly 10 whp and 12+ lb-ft fall off at peak. Now that the engine was lashed to
spec and reset to 0,0 we hand more of a handle on things.

With the vtec AFC 0'ed out and the ECU reset we began our work. All runs were made at 17.5-18BTDC timing... we started at 0,0 and THE CAR made 180/125 corrected with 115/115 at 5252, 178/115tq @ 8400. Not bad... however there were some flat spots across the graph that I was not too happy with. Long story short, by tuning cams -2,-2 +6psi fuel pressure and some happiness with the VAFC... we gained about 3-10tq throught the band and about 6-10whp through the midrange, keeping similar peak numbers. We ended up with about 180+/128 and about 116/116 at 5252. It was my first exposure to tuning with a VAFC, so I am learning for sure... but the mechanical aspect I feel I have a decent grip on.

However I find it funny that this motor called for a -2,-2 on the skunk stage 1s!
Hopefully I have explained this enough that someone could comment on a possible
next step for tuning on this car. The last 500-750rpm or so it dropped 10tq and 5whp up top. When it was lashed incredibly tight it made 123/123 in the midrange with a 4800 VTEC point, lashed correctly this time earlier than 5K (where it ended up) landed firmly on its face to the tune of 15whp/tq down. Overall graph in this car was very smooth and very happy to drive At least its quicker and the valves arent slamming the seats like they were...

I guarantee this thing can put up some numbers in the mid 13s for sure... Id love to take it around Sebring, chances are I will end up watching that day... hehe

 

Haha Mike. Glad you had fun tuning my car in for me. You definitely got the grip on the VAFC for sure. Anyhow i am pretty happy with my results for now. I need to worry about upgrading the nut behind the wheel before any more power gets put into that motor. Thanks again Sarrich.

Mike

 

You have to take into account casting tolerances as well as the margin for error on
the cam gears. Did you compare the cam gears against a stock set? Did you
find the lobe centers on the cams beforehand? This information will help you
a lot on understanding why things end up the way they do.

 

you are right steve. I dont know that as a rule of thumb or even how to degree a cam. This is why I kept the settings very conservative seeming as how I dont fully understand things mechanically, the tolerances at peak etc like you would based on extensive exp. Like I said, I am not highly savvy I understand alot however would like to learn those basic fundamentals of the cams and how to read them etc, degree them out/find the LCAs etc. I dont know how to do that.

not prob mike see you soon, looking forward to sebring , oh by the way yoiu and chris have student IDs and will be $30 bucks at the door for the WHOLE weekend... we might have to camp in the Rs and hang out that night on the track... hehe can you buy my ticket? hehe I like student discounts...


[Modified by MikeSarr_GSR, 4:10 AM 3/7/2003]