Barney1971

Hello all,

Please find the attached dyno chart that shows how the power drops significantly..

What my garage has done are:
- compression check (all cylinders within 3%)
- vacuum pressure (responsive and in normal range)
- maf sensor cleaned
- vtec solenoid filter and gasket replaced, and it worked as detected by scanner
- oil pan cleaned
- engine scanned, with no error detected

My car, L15A vtec 2003-4, was ported and replaced the header.

Please help if you have encountered the same problem/dyno result or had information.

jlk16188

I'm no expert by any means but Honda engineered this little motor to have max torque and power in a small package and did tons of research and testing to maximize this.

I know from experience with D series motors, putting on large exhaust on naturally aspirated motors normally hurts your top end torque, a lot. Looks to me as though the same thing happened to you and your "porting" has shifted efficiency way down as
compared to what Honda engineered.


I dont know what you ported but if you ported your intake ports you may have adversely created too much flow that cannot smoothly enter the head with such small valves. You have made it too free flowing to the intake port and now you are cramming too much into too small of a hole.

Modern, highly engineered engines do not respond well to old school, hey lets just port this while I have it apart, techniques like D and B series do.


Just my 2 cents.

Turbokraft

Was the head removed for porting? It appears that you may have incorrect cam timing as in advanced from stock, notice the increase in low speed torque? Quite the opposite of what you normally see from increased port size/decreased velocity.

Black R

It almost looks like VTEC isn't engaging on the blue plots.

Was the solenoid left unplugged accidentally?

What's the a/f ratio at now?

Barney1971

Tx, this is my third car getting ported there. Last two were all good. In fact, the torque was so flat from 1500 t0 6000, it only fluctuated less than 5% from top peak. They told me they focus on velocity including having smaller pipes than most people consider.

This one, well at least I hope, is going to be better than my other two in terms of %increase in torque and hp. They showed the flowbench results with almost 30% increase in velocity in intake, and 15% increase CFM in low lift, plus only 2-3% increase CFM in the higher lifts.
Exhaust port was also okay i think, with about 40% increase in high lift CFM and 15% in velocity. To me, these numbers are already better than my other results but there is something wrong that hinders the power...

Barney1971

Yes, it was just ported. I already mentioned it to them, but they said it was right on. And, the velocity was high in the intake, a lot higher than exhaust ports. The intake now has about 320 in average velocity, and there are some spots that show 360-365. They explained that was the reason the top lifts only increase by 2-3%. And the cfm low lift was up about 15%,.. some say it was important to have higher low lift in intake.

Well, about porting, I do not have any doubt about them, but perhaps mechanically or electronically they seem not too strong


at first they thought so. they already changed the filter, and the scanner showed it was switched on around 2500rpm. If it was unplugged, the scanner wont say "on", right?

The AF ratio was so bad. It started too lean around 17-18:1 for the first 2000rpm, but fell down sharply to 12:1 after that. And about 10:1 at 4000rpm.
Definitely it will kill some power, but not all, wont it? so if afr was so bad, dont you think the power should still be there over 5500rpm however low would be?

Please if anyone ever sees this kind of ugly chart, share with me the solutions. Based on calculations from flow numbers, I expect 150-160 in hp with 170s Nm. Help me get this, honda lovers. Thanks!

Black R

Fix the a/f with tuning.

Those ratios are terrible.

This NA, right?

Them it should be around 13.5:1 across the board with wide open throttle.

10:1 is far too rich and is robbing you a great deal of power.

claymore

Vtec not opening or ECM in limp mode.

Barney1971

tx, i agree those are bad numbers, all of them. but i dont have no piggy yet (tight budget). The mods are only the header and the porting job (and a knn replacement filter). but definitely i will borrow my friend's piggy

Barney1971

initially we thought it was the vtec filter got clogged. we did clean it up. and i saw on their scanner that the vtec switched on around 2500rpm while the car was on dyno.

what cause the ecm to be limping?

thanks!

claymore

Don't know but that dyno run shows that it basically dies at 4000 and that is limp mode. You could have a working vtec solenoid that still isn't engaging the system. You have to have codes thrown check and see what they are.