I've got a 90 rx7 TII and just put in a ported motor, had it all tuned perfectly but then when it started to get cold out. Car leaned out just at one rpm only, right around 4600. I have 860 cc secondary injectors, Safc II and walbro fuel pump. I've been told to try maybe a hotter spark plug and see if that helps. I've tryed to mess around with the fuel curve over and over. I just can't seem to get that little ping to go away. Any suggestions would be appreciated alot. Thanks- Darin

 

I'm assuming you are running the highest octane gas possible, right?

 

yes, i always run premium. Never had this problem till i came home from school one weekend and was colder by like 30 degrees and haven't been able to fix since.

 

Other than retarding the timing a degree or two... (way too simple and way too cheap LOL)



Since it is only happening at that one RPM section, it is kinda hard to justify water injection. However, AQUAMIST makes great water injectors



Aquamist UK home



There are fully mappable models and there are pre-programmed (unmappable) models) It is just another item to tune but you may be better off with the AQUAMIST 2S. It is fully mappable at incremental RPM. For example you do not have to have the same flow at 2k as you do at 4k so you can really zero in to a trouble range. i.e. if you are detonating at 4500-4750 RPM you can raise the ml/min flow rate in only this range.



Aquamist are also methanol safe (as an anti freeze). This is really opening a can of worms cause tuners argue about the best methanol mix. This will only be a problem if you are in subzero climates or just want to run a methanol mix. Normal mix is around 20% methanol as an antifreeze. However, this may draw attention come race time cause methanol has an octane rating of 130 if I am not mistaken. If you race seriously check your regs to see if this is permissible. However, just water alone is awesome as it has one of the highest if not the highest latent heat of evaporation of a liquid. Which means it is going to stabilize combustion a lot and pull away a serious amount of heat from the combustion chamber. Even though water has no octane rating, by proxy it will boost your fuels octane rating.



It also goes with out saying (but), if you tune with water injection, make FOR CERTAIN you do not run out of water!!!



There have been a few discussions on this forum on water injection, and there seems to be a great debate weather to plumb before or after your IC. That you will have to decide for yourself



Good luck man, keep us posted

 

how do u know it pings?

 

so you're saying that everything before AND after 4600 RPM is fine?

what engine management are you running?

i'll assume that you've tried to get the secondaries to come in a little earlier?