Detonation Observation

[zip]

I agree w/ Turismo, a rich mixture does indeed cause my J&S to activate because of detonation. When I leaned out my mixture a couple of psi down, the knock at low rpms disappeared.

[12SecGSR]

why would too much fuel cause detonation? I have never heard of that before...

[redline]

If it is too rich then you can get a rich miss. ie too much fuel and not enough air in the chamber for the plugs to light it up.

Are you getting the lots of fire out the tail pipe? That is a good sign that you are close to a rich mixture.

k

[Turismo]

I might be completely off here but..

If TOOOO much gas is being added it could be compared to raising compression because of more molecules in the combustion chamber will take up more room and make the air in the cylinder harder to compress, therefore raising compression (slightly) and causing more detonation, kind of like how carbon deposits can reduce combustion chamber size and cause higher compression.

Side thought.. If this is true, wouldn't water injection have the same problem (added mass in the cylinder).

Just throwing it out there.

[Holden]

Turismo: That same idea came up in a discussion I had with a bunch of Nissan guys.

We all pretty much agreed that it would take a boatload of gasoline to raise the compression enough to affect detonation.

If the other idea, (too rich and hard to spark up), is true, I wonder if folks with aftermarket ignitions have any thoughts to add.

Greg

[plumvtec]

You guys keep mentioning detonation, but there is something else to consider which is pre-ignition. This causes the fuel mixture to burn too soon.
I'm not saying that the theory imposed is not correct, rather you left out another variable.
Good observations on the excessive fuel.We'll get to the bottom of this yet.

------------------
'96 JR6 GSR Sedan (black currant pearl) FOR SALE !
'93 Honda CBR 900RR
-------------------------

[Turismo]

After getting some BIG injectors a couple months ago in hopes to run the OE regulator and stock fuel pressures by using my PMS to deal with fuel tuning I had problems with a "rich" engine code and haven't had time to mess with it since. But in effort to lean out the mix then I put the OE fuel pump back in and hadn't switched it since. I since then have been able to tune out 99.9999% of the detonation I had previously seen on the J&S. Yesterday, after a couple long top end pulls I noticed that my fuel pressure was dropping off a little on top (although staying rich on the A/F)so I put the HO Walbro back in to be on the safe side. I have now noticed the detonation I used to see has returned. Could this be a problem that too much fuel or too high a volume or flow is causing a problem with returning the fuel to the tank and causing some sort of turbulence inside the fuel rail resulting in this detonation that wasn't present before??
Maybe it is just the fact that it is getting more fuel now and needs to be tuned back down but I wouldn't expect to see a real difference where it occurs (tip in - mid throttle) because pressures are the same there.

Is there a fuel pump that flows the same as the OE model but will still flow correctly at the 90+ psi mark??

What psi will the Walbro JR sells good up to??

Food for thought.

[JRCivic]

Turismo,

I have just the pump for you... the Walbro GSS-250.

It flows fuel all the way up to about 110 psi... and the flow rates are just slightly higher than the OE GSR (actually about 25% more) across the entire graph... that is until about 60 psi where the OE pump takes a dangerous nose dive.
E-mail me and I will make you an unbelieveable deal on it.




------------------



'93 Civic Si H/B with B18C1, JRSC @ 8psi
Best 1320: 12.68 at 110 mph