Hopefully you guys can help me out here.

I'm going through the street tuning process with my new engine. I'm having some small pinging issues which I'll describe later. I'm using the following tuning aids:

Hondata S300
PLX R-500 WB O2 sensor and knock display (with headphones)

The build details are as follows:

Cams: Skunk2 Pro1 (set to Skunk2 specs for timing)
Valves: Ferrea +1mm intake and +0mm exhaust valves
Pistons: Wiseco 5cc
PCV: Endyn breather on block with PCV routed to intake
Plugs: NGK platinum (temp = 7)
Intake: Mugen
Exhaust: Spoon header + Mugen exhuast + highflow cat
Injectors: RC440

Compression Ratio = 11.8 (Compression on engine reads 280+/- 2psi across all pistons)
Fuel = Sunoco 94

I’ve inspected the plugs daily and they always look good. Took the car to the builder yesterday and he did a visual inside the combustion chamber and it looked good.

The issue:
When accelerating (both lightly and WOT) between 2000-3000RPM I can hear slight pinging in the engine. This is particularly true when I'm in a tall gear and try to lug the engine up to speed. I've tried adding fuel and reducing timing without any noticeable effects. I’ve tried changing the throttle tip in trim but that also doesn’t seem to help. The pinging can be heard both in the headphones and in the cabin.

I've tuned the A/F to be pretty much flat in this region of the map. At low load the A/F is 14.7 at medium load it is 14.0 and the 4 right most columns are at 13.2.

Besides this one RPM region the engine does not appear to exhibit any pinging and appears to runs very well.

I've included the ignition and fuel maps for the low speed cams. You can clearly see that the breathing of the engine is changing very much during this region and it may be that reversion is diluting the intake charge causing the pinging.

Any thoughts on what I might do to eliminate this would help.

I want to get the street tune nailed down before I head to the dyno and pollish up the top end.

Thanks a bunch!!
Doug







Modified by BABY NSX at 7:05 PM 3/29/2007

 

Take more timing out from 2000-3500.

 

Thanks for the reply Don!

I'll give that a shot and see what where that goes. I think I may have removed too much fuel in the last 4 colomns bellow 2000 RPM. I think that artifact was left behind when I was adding fuel between 2-3k but purhaps the sharp edge in the fuel curve is giving the ECU fits. My original base maps which were for Pro1 cams did not have such a steep peak. of course capturing those load points on the road is not so easy...

 

ok from what i can see your fuel curve is not linear, meaning if you look at column 5 for example
2500 - 247

2750 - 258


3000 - 258

this should be going up and it actually starts to go down after 3000 wich is not right, and this is the same for all the columns higher 6-10 . also taking out some timing especially in columns 2-5 will help.

 

There used to be a bug where the cranking fuel and tip in fuel were swapped. I dunno when/if this got fixed. What is the A/F when it's actually pinging? If that's ok then pull more timing...

 

Air fuel ratios always seemed to be ok... but I think the problem may be stemming from both too much timing and a wonky looking fuel table.

I've done a rough smoothing out of the fuel table from 0-4000RPM while trying to maintain the same area under the curve. I have not yet done a careful session to optimize this but the A/F numbers seem to all be on the slightly rich side (which I am comfortable with for now).

I also "shifted" the timing advance curves a few 100 RPM so the effective timing between 2000 and 3500RPM has been reduced a few degrees.

The light pinging under moderate throttle tip in now seems to be gone. I still notice that when the car is lugging out of the hole in 4th or 5th gear at WOT I do hear some added noise (pinging?). This seems to be a steady state condition so I'm not sure if throttle tip in parameters will help out here.

I will try to remove some more timing at WOT between 2000-3500RPM and see where that gets me.

Thanks again!

 

Why are you at WOT at 2-3000 RPM?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by DonF &raquo;</TD></TR><TR><TD CLASS="quote">Why are you at WOT at 2-3000 RPM?</TD></TR></TABLE>

hehe... clearly I never plan on driving at these load points but if I can improve the operation of the engine here then I'll feel more comfortable about the overall tune.

It may be that the overlap in the Pro1 cams does not make WOT very tuner friendly at these low engine speeds. The increased dilution of the intake charge may simply be too great. Because this is an impractical load point for the engine I'm prepared to live with this if it simply can't be tuned out.

Solving the issues under light load was my biggest concern which seems to be working well now.

 

I doubt it is increased dilution at low revs. It is the fact that the Pro primarys allow the cylinder to be filled more as they are a more aggressive cam, theirfore require less timing as dynamic compression is up. IMO

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by DonF &raquo;</TD></TR><TR><TD CLASS="quote">I doubt it is increased dilution at low revs. It is the fact that the Pro primarys allow the cylinder to be filled more as they are a more aggressive cam, theirfore require less timing as dynamic compression is up. IMO</TD></TR></TABLE>

Ok... I see your point. If this is true then simply removing timing until the knock goes away should be possible. I will continue down that road.

My thinking was that if the intake charge is too diluted then it might be messing with the normal burning of the fuel.

 

Do you have a load bearing dyno available to you in your area? It is 100x times easier to lock the car town to that rpm/vss and emulate the condition on a load bearing dyno. You can literally step on the throttle to generate this condition, and then adjust the fuel/ignition to not only stop the knock but also maximize torque.

 

I'd get rid of the platinum plugs.

 

try using different gas.. i used sonoco94 once and it sucked ***