Fuel Mulitplier in Crome questions????
 

One of the basemaps i recieved from Xenocron got me started and is running pretty good in Vac and light boost, so i am tuning it and i noticed that in the fuel mulitplier the new injector size is 353cc and i have 450 cc injectors. Do i need to leave it at 353 and tune it or change it to 450 and tune it?? I read somewhere on pgmfi that the fuel multiplier is not totally correct. What do you suggest??

THanks!

Re: Fuel Mulitplier in Crome questions????
 

leave it where it is and tune the tables....

that is probably an old skool bin...before Fuel Tools.

The Fuel Tools functionality has been improved since then...

Re: Fuel Mulitplier in Crome questions????
 

Yea, I notice that on a lot of the maps I get from the crome bin directory, the injectors are either stock, or some weird number. But the notes in the directory say otherwise.

Re: Fuel Mulitplier in Crome questions????
 

What about current versions of Crome? Is it safe/ok to rescale the injectors to thier actual values, or do they still require fiddling with??

Re: Fuel Mulitplier in Crome questions????
 

Okay, sounds like a plan :1. But can someone answer the other dudes question

Re: Fuel Mulitplier in Crome questions????
 

It's actually a good thing to "under scale" your injectors, it helps with tuning your idle and such when compared to injector latency times for large injectors. It also tends to give you room up top when you start getting close to the "99%" duty cycle time. Do what Chris says and leave it where it's at.

Re: Fuel Mulitplier in Crome questions????
 

i guess i'm confused here a bit. you underscale it so you run the wrong injector latency times? can you elaborate a bit more

thanks

-Luke

Re: Fuel Mulitplier in Crome questions????
 

I don't understand either. Latency is a due to the injector being physically larger.

Re: Fuel Mulitplier in Crome questions????
 

I can buy that if you've got an old version of software that doesn't support fuel tools, but I think (as well as read) that it is paramount that you input the proper static injector fuel flow rating and tune injector battery offsets properly in order to maintain consistent AFR's in a multitude of atmospheric conditions. Improper injector dead times will make tuning a real hell.

Re: Fuel Mulitplier in Crome questions????
 

Something else I noticed today while tuning.

I started with a p72 rom, scaled for 450cc injectors yada yada added all the necessary plug ins.

Now, the only thing different I did this time that I've never done before is change the engine capacity in the fuel multiplier. I used 2156 since I'm tuning an f22.

Instead of scaling by .533 it did .7xx or something like that.

it actually was a better basemap than any other basemap I've made for f22's.

Anyways, when I reopened the bin I noticed that under new injectors, there were 333cc injectors, not 450's.

I didn't mess with it because the car runs perfect. But I was just wondering why it does that.

Re: Fuel Mulitplier in Crome questions????
 

Wierd.
Thats good to know for the future, my motor is bored 20 over, I wonder if that small amount of displacement change will make a difference.

Re: Fuel Mulitplier in Crome questions????
 

Actually it tends to make life easier and gives you a "buffer zone" type of safeguard. Think about it...battery voltage at idle is normally around 12.5~ volts which causes a "slight" delay in how fast the injector can open. This adds to the hell of tuning idle, which I'll go over below.
Scaling from a 240cc injector to say a 450 or 560cc size only changes the injector times to the "enlarged" ratio, not an adjusted ratio. Going from a 240cc to a 560cc is over double the fuel charge, so naturally if you put in the new injector size value as "560cc" it will cut your injector open times in half (and a hair more) for the entire map. Add in the latency of a much larger injector than stock, and you can see where it becomes hell to tune. The injector pulse is so fast that the injector has almost no time to open due to it's large latency "lag time", and the lower battery voltage at idle continues to hinder it. In the higher rpm range, voltage increases slightly and can open the injectors a bit faster. Therefore, if you set the injector size lower than what it's rated at (say 510cc instead of 560) it allows for a slightly longer injector pulse signal due to less of a ratio percentage applied against your fuel tables. The longer it's open at idle, the more fuel will come out of the injector in regards to it's inherent latency time. It makes tuning your idle much easier and keeps your your times to a semi-normal rate, and through the rest of the map you will end up cutting out a small amount of fuel time instead of normally adding to it. It allows for nice rich basemaps and easy control over fuel when fine tuning. Also, it adds the benefit of never running over a certain duty cycle if you keep your maps under 100% DC. Typically, injectors aren't really meant to hold times of over 85%DC, and this way adds a small bit of buffer just in case you do end up a little above the DC time you want.
More than likely Chris did the injector sizing this way to help you get up and on your way without having the typical idle latency issues normally associated with larger injectors.

Re: Fuel Mulitplier in Crome questions????
 

Well my idle sucks, as in it idles up and down sometimes and sometimes its sits perfect at around 800rpms. I am running a P30 codebase and Chris let me know to try a p72 base. I did try that map with the 450 cc injectors in high altitude i think from denver or something and it was tuned with 450 in the fuel multiplier. My car ran extreamly rich and it set a check engine light right away. I didn't check what code it was but if i remember correctly it may have idle'ed better but i just went back to what i started with. I think i will just leave it with 353cc cause it runs awesome other then at idle. :6

Re: Fuel Mulitplier in Crome questions????
 

why not just fix the idle your self? play with the idle iacv slider bar and try to get the car idling stock, shouldn't be that hard.

Re: Fuel Mulitplier in Crome questions????
 

If your car idles fine with a stock ecu, then messing with the slider won't do anything.

If the idle is surging, you're probably too lean. If it were too rich, the motor would die.

Re: Fuel Mulitplier in Crome questions????
 

Oh no, i have it around 14.5-14.7 at idle. I will idle perfect sometimes and it will surge up and down sometimes. It will surge right after the rpms increase with my foot....then i let off and it idle surges for like 30 seconds to a couple minutes and then it just smooths out to a perfect idle between 750-800rpms.... then as soon as i touch the gas it will do it again. It could be my iac, i did pull it and cleaned it out real good with brake clean but maybe its still crapped out.... its the original one with 80,000 miles. It did the same thing the first time i started it up when i was runnig a SAFCII and the 450s after the turbo was installed but after those first initial start ups it never did it again while i had the afc. Now my car sat for a couple months with the transition of the afc to obd1. I have messed with the fuel maps alot, rich and lean and stoich but never fixed it. I think it may have done it in open loop, i don't remember for sure, SO if it did it in open loop, then it could be the IAC???? When i pulled it the screens were nice and clean and the pintle moved freely, but i cleaned it anyways. Dang i wish i had a test one so i don't have to shell out some money for a new one if its not the problem. AS i read through what i wrote..... it sounds like i need to replace the IAC. what do you think???

Re: Fuel Mulitplier in Crome questions????
 

Have you checked all over for a vacuum leak? I'm using an obd0 head & intake manifold on a newer block, and I have caps on a few nipples from the obd0 setup.. awhile ago one came off and my idle would surge a few times after i let off the gas and then sit nicely at idle.. I thought it was something wrong with my crome basemap but i ended up finding one of the caps fell off a nipple and was leaking pressure. just a suggestion.

Re: Fuel Mulitplier in Crome questions????
 

I will spray some brake clean around the intake and vaccuum lines tomorrow, i visually looked and didn't see anything and i cant hear anything but we both know that it could still have a leak. I hope i find it. Thanks for the advice cause i really havent tried that yet. :y

Re: Fuel Mulitplier in Crome questions????
 

To rule out the iacv, bypass the coolant lines.

Re: Fuel Mulitplier in Crome questions????
 

I would just adjust the iavc slider. I had seen a couple of cars idle fine on stock ecu but can't idle without surging on crome. We usually just adjust the iavc slider and get it close to stock. But to each his own. GL

Re: Fuel Mulitplier in Crome questions????
 

I have not messed with the iac slider and have not bypassed the coolant lines yet. I did spend some time looking for a vacuum leak, checking all my vacuum lines and factory vacuum lines. I sprayed all over the place with brake clean and nothing. at idle around 800 rpm i am pulling 22-23 hg. I will mess with that stuff later, i still have not tryed a p72 base yet either.

Thanks dudes!!!

Re: Fuel Mulitplier in Crome questions????
 

None of the suggestions on here helped me with my idle issue but it is now fixed. Heres the story..... i didnt like the way my junk yard DSMs were flowing, seemed like one cylinder plug was a little lighter (whiter) then the other 3 and my AFR's would all of a sudden run lean and then back to normal in vacuum everyonce in a blue moon :l . Well i wasn't gonna get them flow tested and redone because the cost was close to buying new ones from Xenocron. SO i ordered Prescision high impedence 440s and clips, removed my radio shack 10 ohm resitors and put those bad boys in. Night and day difference, the idle has not surged once since i started it, they are a little quieter for my det cans, and my afrs are constant. Needless to say my DSMs will be on ebay, just warning the HMT community. >:D

another quick story i was at the track last night in SA cause pinks all out will be here in a couple weeks (im not racing- to slow) but anyways i talked to a guy who had a s2000 turboed running AEM management at 15 psi. Anyways at idle he had 11.7 afrs. So i asked him, who tuned his car and he said he did. Well he has his car at 11.7 through both sides of the maps and he is running 12.9s. What a waste of gas and speed. He must have gotten his tuning lessons at quicky lube. :y Im not saying i am the smartest fish in the toilet but that is pretty bad. :3