Drax240z Posted December 21, 2004 Share Posted December 21, 2004 I read some figures recently, and I don't recall where. Somewhere it was stated that every 10*F temperature drop in intake temperature basically equalled a point of octane. (ie: lower temp = same effect as more octane) Has anyone else experimented with this and come up with a correlation they want to share? I am curious to know how sensative my engine is compared to air inlet temp. (ie: where the air filter is) I know cooler is better. How much better is what I want to know. Is it worth hours of experimentation to drop intake temps by 20*F? (I would expect so, but...) Any insight appreciated. Quote Link to comment Share on other sites More sharing options...
Cody 82 ZXT Posted December 22, 2004 Share Posted December 22, 2004 Heres some information I found in a book I have. Supercharging, Turbocharging, & Nitrous Oxide by Earl Davis and Diane Perkins-Davis pg. 116 Under the "Consider the following" on the page sideline. "Each 25* reduction in charge air temperature reduces octane demand by 1 point." There are also several other octane related points to ponder in the section aswell. If my stupid scanner was working right I'd just scan the page and post it. Quote Link to comment Share on other sites More sharing options...
Drax240z Posted December 27, 2004 Author Share Posted December 27, 2004 Cool Cody, at least that gives me some sort of rough guideline to go off of. I am going to measure my air intake temps and compare with a bunch of other locations in the front of the car. I may just make a shroud for what I have too. I think I can probably drop my intake temps by 25* though, as my intake is somewhat behind my radiator. (down low, but it gets a mix of cool & hot air) Quote Link to comment Share on other sites More sharing options...
Guest ON3GO Posted December 27, 2004 Share Posted December 27, 2004 intake temps as in air filter or the intake maifold itself? i always wondered if you heat wrapped the intake manifold if it would keep that cooler also... im also building something of a shroud for my air filter (i mean.. what air filter lol) but i dont have much room as my piping is hugh and so is my fmic. mike Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted December 31, 2004 Share Posted December 31, 2004 Okay but now answer me this... How does the intake temp affect the fuel mixture? If you reduce the intake temps 25*, and effectively up the octane of the fuel by one full point, how much do you effect the a/f mixture, assuming your fuel system does not compensate for this at all? Wouldn't the change in mixture (getting leaner for colder weather) do more harm than the 'raise in octane' would do good, as far as preventing detonation? Quote Link to comment Share on other sites More sharing options...
Drax240z Posted December 31, 2004 Author Share Posted December 31, 2004 Most modern EFI systems take air temp into account, so no worries there for me. I would say as a rule though, the cooler the air you get, the better. I don't think there is any reason, even with an archaic EFI system to want warm air at all. Tell me that your car doesn't respond well to cool weather the way it is now. Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted December 31, 2004 Share Posted December 31, 2004 no no of course you don't want to WARM the air Okay here is why I ask. I know even my stock '81 EFI does have the means to measure air temp and compensate for that. However, at the boost level I'm running (14psi) I also know that at WOT/higher RPM, the fuel system is completely maxed out, no longer really compensating for temp or anything else for that matter... just running the injectors at their maximum duty cylcle. I run a RRFPR to augment my stock fuel system and give me the fuel I need to run 14psi all the way to redline w/o running lean. However, the RRFPR has no way to compensate for temperature at all. And since the EFI doesn't know I"m sneaking extra fuel in there via the FPR, the EFI won't compensate either, by lessening the pulsewidth and not running full duty cycle... so either way... I get no compensation for air temps at WOT/full boost/high rpm. So I always worry... should I be richening the setting on the RRFPR when it's colder out, to prevent detonation from lean running? Or can I just leave the RRFPR setting, and let the colder air, by the mere function of being colder, prevent the detonation itself? Quote Link to comment Share on other sites More sharing options...
Cody 82 ZXT Posted December 31, 2004 Share Posted December 31, 2004 So I always worry... should I be richening the setting on the RRFPR when it's colder out, to prevent detonation from lean running? Or can I just leave the RRFPR setting, and let the colder air, by the mere function of being colder, prevent the detonation itself? When I used to run the almost exact same setup as your only with a bigger turbo I would have to dial in more fuel if the temp was 60*/70* on day and then 20*/30* the next. Not that this happens often but, does happen in the Dallas area atleat once a year in the winter. Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted December 31, 2004 Share Posted December 31, 2004 I didnt' get my W/B O2 for Xmas as planned so I'm still kinda stuck for tuning this thing.... I haven't been driving much since it got cold out, but every once in a while I take it out to stretch it's legs, keep the fluids fluid and such, and wonder if I'm running way too lean in the 40-some degree air. When I tuned it last on the dyno was like a 90* day..... I still have not heard a ping. Quote Link to comment Share on other sites More sharing options...
Bernardd Posted January 13, 2005 Share Posted January 13, 2005 http://www.mustangworks.com/articles/misc/GasFAQ.html Section 7 is where you want to go. Quote Link to comment Share on other sites More sharing options...
Len Posted January 13, 2005 Share Posted January 13, 2005 Really GOOD stuff in that website Bernardd Quote Link to comment Share on other sites More sharing options...
SHO-Z Posted January 13, 2005 Share Posted January 13, 2005 Check is good reading http://www.superchargeronline.com/content.asp?ID=104 Quote Link to comment Share on other sites More sharing options...
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