Originally Posted by Originally posted by acatak
I just put in my ITR cams and skunk 2 cam gears. I was gonna tune them on my own for now becasue im not goning to go dyno my car until im done modding it. What id a good way to tune them myself? Also, should i advance intake and retard exhaust? I want to knock off the most time on my 1/4 mile so im sure top end is better.
Also, I have I/H/E also right now. What do you think would be a good next performance mod. I dont want to do any more internal work. SO i was thinking car, FPR, or VAFC. Thanks for your help
"What is a powerband?" thread
To shift or move the powerband up higher along the rpm range
(for 1/4 mile et. improvement), you need to increase the overlap.
You do this by tightening
the lobe separation angle (LSA) between the intake cam's and exhaust cam's lobe centers with your aftermarket adjustable cam gears . When you tighten the LSA, you increase cam overlap
If you want a higher powerband location, you tighten the LSA by rotating the intake and exhaust cam gears in opposite directions from one another in steady precise increments. The trick is to find the best overlap for your particular engine's package of parts and unique way of breathing compared to everyone else's.
EFFECT OF TIGHTENING THE LSA WITH ADJUSTABLE CAM GEARS
Hp and Torque Curves with
Dots = Tighter LSA
Without Dots = Wider LSA
Wider lobe separation angle (no dots) produces more midrange torque but with a loss of upper rpm and peak torque.
Narrower lobe separation angle (with dots) produces more high rpm range and peak torque but with a loss of midrange.
Less LSA increases intake and exhaust valve opening overlap which creates more scavenging and a stronger upper rpm powerband.
Less LSA [or more intake and exhaust cams overlap] is better for a racing engine than a high performance street engine. The idle suffers as you add more overlap since there's not enough vacuum at idle rpm.
SUMMARY OF THE EFFECTS OF TIGHTENING LSA
1. Moves Peak Torque to Higher RPM
2. Increases Maximum Torque
3. Narrows Powerband
4. Builds Higher Cylinder Pressure
5. Increase Chance of Engine Knock
6. Increase Cranking Compression and Effective Compression
7. Idle Vacuum is Reduced and Idle Quality Suffers
8. Open Valve-Overlap Increases
9. Closed Valve-Overlap Increases
10. Decreases Piston-to-Valve Clearance
Obviously, widening the LSA (decreasing overlap) does the opposite to these.
Aftermarket Cam Gears: What To Look For When You Shop
Stock cam gears cannot be adjusted. You must purchase aftermarket adjustable cam gears. Good ones are:
1. light so that they don't add valvetrain mass (anodized billet aluminum)
2. have good cam gear bolts to hold down the cam gears to prevent them from slipping after you've torqued them down (usually these have more than 3 bolts but there's a balance between having too many bolts so that it becomes an inconvenience during tuning and not enough to prevent slipping. I'll put up with inconvenience since slip prevention is a priority.). The cam gear should be rigid or surface-hardened enough to prevent the bolt from sinking into the cam gear surface.
3. have etched-on, clearly readable, easy to understand, highly accurate markings. Painted on markings are easily worn off. if the 0 degree mark is not TDC what good is the cam gear? Some cam gears makers have not double-checked (quality control) their TDC markings against the stock TDC marks and degree the cams after their cam gears have been installed to see if the 0 mark is truly TDC, so be cautious on install and check.
Have you checked to make sure that INTAKE 0 degree and EXHAUST 0 degree markings on those cam gears were indeed set at TDC?
on a tuning session on the street or at the strip, I suggest that you do the cam gear tuning by going with a friend in the passenger seat with a stopwatch, if you don't have a datalogger that records speed and elapsed time. Do some wide open throttle acceleration runs at the 1/4 mile strip on a test & tune day.
The point here is that , for each cam gear setting, do your timing over the exact same stretch of road and over the same exact distance. Have your friend time how long it takes you to go from say 30 mph to 90 mph. Do 2 runs for every setting. You want an objective measure ,like an acceleration time, to tell you if the setting is good for your particular engine. Acceration is the change in speed over the change in time. You want a higher number if the cam gear setting is good. A change of 1 tenth of a second or more consistently is good.
Don't rely on the butt dyno. It's only sensitive to changes in the early part of the rpm range.
DO NOT COPYCAT SOMEoNE ELSE'S CAM GEAR SETTING
Each person's engine will have a different optimal cam gear setting for it. Just because someone has the exact same model Integra and parts as you, does not necessarily mean that their engine and yours behave identically. Variations in performance can occur simply from minor differences in assembly at the factory, engine break-in procedures (if any) by the owner, and owner maintenance.
I would go 2 camshaft degrees at a time starting with the intake cam, since it also determines the reference baseline ignition timing as well (connected to the distributor) . Do 2 runs per setting over the same track distance.
When you stop seeing an improvement in the elapsed time in between your 2 set mph points, then go back to the best setting.
As for the "next best part" for your engine, I really don't think along those lines. I choose my powerband location and power goals first, and get parts that have designs or specs that will fascilitate getting those 2 goals.
Sometimes you have to do some math to get the exact specs for these but in general, high powerbands like single stage IM's and 4-1 headers with big diameter primaries & collector , for instance.
If you don't have a VTEC controller, you'll definitely need one, since the ITR cams will want a higher VTEC point, higher VTEC fuel table starting point, and different fuel tables than your stock GSR VTEC point and fuel tables.
I think we've covered quite a bit about FPR's before and when to get them and so, those threads can be easily found on a search. You can't richen the fuel delivery using a VTEC controller at full throttle and so, you'll need an FPR to richen and use the controller to lean down in the rpms that become overly rich after the FPR has been set.
DoN'T FORGET TO RESET YOUR IGNITIoN TIMING BACK TO YOUR INITIAL SETTING USING AN IGNITIoN TIMING LIGHT AFTER THE INTAKE CAM GEAR HAS BEEN CHANGED AND YOU ARE DoNE CAM GEAR TUNING.
WARNING: If you advance the intake cam gear and retard the exhaust cam gear too far, you risk piston to valve contact. Remember 1 cam gear degree = 2 crankshaft degrees and so you exceed 8-10 cam gear degree change at your own peril, unless you have precisely degreed your cams and know exactly how many degrees max. advance/retard you have to play with.
good luck with your modding.
Dyno Tuning Basics Article