polarisman14 Posted September 21, 2015 Report Share Posted September 21, 2015 Hello, I have a buddy helping me with me with my VE table and his required fuel is 4 points lower than mine for idle for whatever reason. What is the relationship between VE and required fuel? As in can I use his VE table and scale it (richen it) up a certain percentage across the board to compensate for the difference? Or does it vary by cell? Thanks! Link to comment Share on other sites More sharing options...
button Posted September 21, 2015 Report Share Posted September 21, 2015 http://www.megamanual.com/v22manual/mfuel.htm read that. In short, you can use any table you want and scale it however you want. Does he have different injectors, engine size, number of injectors....?Then consider any other differences in your setups (turbo, piping, IC, air filter, manifold setups, NJV head, etc..) and you will start to realize why table sharing isn't always the best idea when trying to get YOUR tune dialed in if you already have a base map. Link to comment Share on other sites More sharing options...
scott87star Posted September 21, 2015 Report Share Posted September 21, 2015 Do read what Button posted, it's the long version and worth a view. The short version is the required fuel value is the pulse width required for stoich fueling at 100% VE. Of course, everything is relative. Link to comment Share on other sites More sharing options...
polarisman14 Posted September 21, 2015 Author Report Share Posted September 21, 2015 (edited) ^^I will definitely read that. I'm in sponge mode right now and trying to soak it all up. I took the previous tune from you (scott) and finally got the base idle down to a buttery smooth 950rpm at 12.7:1AFR, trigger angle is all dialed in, 50psi of fuel pressure. Essentially, I need to drive the car 60 miles round trip or a touch more to get the car inspected at a buddy's shop who is moving cross-country in a couple weeks and closing up shop. I need to ensure that the tune will be safe to get the car there and just want to know what simple changes I can take to ensure it won't be timed too far advanced (or retarded) and the fueling is in an OK spot as well. I'm now running 50psi of fuel pressure versus the initial 60psi, and now running 8:1 CR vs 7:1 before so I would think the timing across the board (generally speaking) would be too far advanced and the fueling will be on the lean side as well. Am I correct in this? When I get the car back from the inspection run I can get into the fine tuning aspect but I need to know it won't blow up on me just gently driving there and back. My thought process with table sharing is that his setup shares my fuel injector and pressure, compression ratio, very similar turbo and IM, exhaust size, etc etc and the main differences are he has a fully built and machined head and a few other odds and ends. I assumed (perhaps incorrectly) that a setup like his that shares the same compression ratio and 90% of other stuff would be closer to target values than my old tune as the compression ratio and fuel pressure were both off. It seems to idle great on this tune (my old one) and once I have a chance to drive it around and take a couple datalogs I can confirm the on-road performance. Edited September 21, 2015 by polarisman14 Link to comment Share on other sites More sharing options...
speedyquest Posted September 21, 2015 Report Share Posted September 21, 2015 My two thoughts reading your last post is that your fuel pressure is too high (unless you have aftermarket injectors that require that pressure) and that your idle A/F ratio is far to rich. I'm interested to hear what put you on that path though as I definitely don't know everything and would love to hear your thought process on it. Link to comment Share on other sites More sharing options...
polarisman14 Posted September 21, 2015 Author Report Share Posted September 21, 2015 (edited) The industry adopted a standard in most cases of 3 bar (43.5psi) or 40psi fuel pressure. While that is a good number for most setups, people discovered a long time ago that you can run higher pressures in order to gain higher HP potential out of their injectors while not exceeding duty cycle (most limit duty cycle to 80-85% from my understanding). In my case, running a walbro 255 pump at 50psi on 75# injectors should be more than enough to supply fuel to my 400whp goal, while I am not sure if 40psi would be enough. It's pretty widely recognized with these cars that if you aim for a stoich (14.7:1) AFR at idle it'll burp, pop, fart, and make all other kinds of unpleasant noises. A ~13:1 AFR makes these cars idle pretty happily and smoothly and result in a pretty low KPA (read, higher negative in/hg of vacuum) which is what you're looking for. Mine idles at 17 inches of vacuum at 950rpm with a TEP street/strip cam which I think is pretty decent. Edited September 21, 2015 by polarisman14 Link to comment Share on other sites More sharing options...
button Posted September 22, 2015 Report Share Posted September 22, 2015 (edited) A properly setup head will alter the fuel requirements a bit. The calculator just gets you a base line. So lets start with a base line...Are you batch fire, or sequential? What do you have, and what did you calculate? Also, brands make a difference, RC/denso will react different than FIC/rochester, and so on. As far as driving it, with someones map, if you paid for Tuner Studio (I recommend you do) you can just run auto tune while cruising, but stay out of boost. Blowing up an engine rarely happens while cruising. Edited September 22, 2015 by button Link to comment Share on other sites More sharing options...
polarisman14 Posted September 22, 2015 Author Report Share Posted September 22, 2015 Yeah I already have a full version of TS and do plan on taking some datalogs of the way it reacts right now, then using VE analyze at some point to make changes. It seemed OK on the way home but with no datalog from that trip to confirm I just don't know. Once I get home I can take a look at the tune and answer your questions. Thank you for taking the time to respond. Link to comment Share on other sites More sharing options...
polarisman14 Posted September 22, 2015 Author Report Share Posted September 22, 2015 Batch fire--1 and 4 fire at the same time and 2 and 3 fire at the same time. Honestly not sure brand of injectors as I bought them used as part of a package deal for the FIP IM and Megasquirt controller from Boosted88TSi (Jason). My required fuel that I came up with is 7.5, calculator shows 6.4 using 2598cc (bored .030" over), 4 injectors, 75lb/hr and 12.7:1 AFR. Should I keep my required fuel where it is, or go with what the calculator suggested and change the TB set screw to compensate for idle speed? I'm not worried too much about the engine but I'd still like some reassurance as I dropped 10psi of fuel pressure and added a full point to compression ratio. That makes me assume it'd need more fuel. Link to comment Share on other sites More sharing options...
StarquestRescue Posted September 22, 2015 Report Share Posted September 22, 2015 (edited) Your buddys ve #'s are likely higher to compensate for the using a smaller required fuel. Assuming things are as similar as you described. Edited September 22, 2015 by StarquestRescue Link to comment Share on other sites More sharing options...
polarisman14 Posted September 23, 2015 Author Report Share Posted September 23, 2015 (edited) Yeah but my required fuel now is a point less than it was when I was running the same injectors with the stock compression ratio and 10psi MORE fuel pressure. That's what doesn't make sense to me. I thought essentially the goal when setting required fuel was to achieve the lowest kpa possible with a respectable AFR and idle rpm which in my case would mean a lower required fuel number coupled with backing the idle set screw off to compensate as little as possible with the butterfly valve. I think I have done that as my ADC count for the TPS is about 40 counts lower than it was before. I can try going leaner and dialing the idle set screw back even more, just not sure how much more room there is before the set screw isn't hitting the stop anymore. Edited September 23, 2015 by polarisman14 Link to comment Share on other sites More sharing options...
CaliConquestAlex Posted September 23, 2015 Report Share Posted September 23, 2015 My req fuel is only 2.0 because i have 95lb injectors. If i go higher on the req fuel, my ve numbers are too small down low to have enough resolution for tuning idle. Link to comment Share on other sites More sharing options...
polarisman14 Posted September 23, 2015 Author Report Share Posted September 23, 2015 Wow. That's nutty. I'm trying my buddy's REQ at 5.8 and seeing if that helps at all. Right now my required fuel and VE/ign maps are NOT jiving. lol. Link to comment Share on other sites More sharing options...
scott87star Posted September 23, 2015 Report Share Posted September 23, 2015 You're way overthinking this; start the car, warm it up, get it at the idle speed you want and adjust required fuel until you get the AFR you want. Don't obsess about what the value is, drive. Link to comment Share on other sites More sharing options...
polarisman14 Posted September 23, 2015 Author Report Share Posted September 23, 2015 If I could put a thumb up here, I would. Thanks for putting my mind at ease, Scott. I was just worried about the timing, too. Link to comment Share on other sites More sharing options...
speedyquest Posted September 23, 2015 Report Share Posted September 23, 2015 I posted up the second tuning video, take a look at it. It might help you out... maybe not. Link to comment Share on other sites More sharing options...
polarisman14 Posted September 23, 2015 Author Report Share Posted September 23, 2015 Thank you! Link to comment Share on other sites More sharing options...
polarisman14 Posted September 23, 2015 Author Report Share Posted September 23, 2015 Here's another one: My car keeps sporadically fouling a plug. I'm sure it's the same one as the other ones don't seem to and driving will eventually make it "un-foul" but it seems to happen almost exclusively on warm restarts. Any idea what could be causing this (is it tune related, or just a bad plug?) Also, what's recommended to run for plugs? I'm running NGK BPR7ES gapped at .030" but what I took out of there was BPR8ES with the same gap... Link to comment Share on other sites More sharing options...
speedyquest Posted September 23, 2015 Report Share Posted September 23, 2015 (edited) I think a bit more information would be useful. I'm guessing you already know that fouling is due to richness, so the initial reason is obvious but also keep in mind that once a plug has been fouled pretty badly it may never work as efficiently again which may be causing it to continue to foul out. Kind of a self induced continuation of the issue. As far as the plugs go you will hear most people insist on you using BUR7EA-11 plugs. I use them and it seems to really make a difference. FYI the plugs are NGK 7031 Edited September 23, 2015 by speedyquest Link to comment Share on other sites More sharing options...
polarisman14 Posted September 23, 2015 Author Report Share Posted September 23, 2015 Yeah it would not surprise me if it were due to richness as it was pretty rich under load--I was having some electrical issues that caused all sorts of problems including but not limited to a discrepancy between the AFR on the gauge and AFR displayed in MS. What further complicates this is that I swapped out these plugs for the old ones I had kicking around for emergency and the problem, while lessened, didn't go away completely. I guess it's possible that it is a thermal issue with the plug wires or fuel injectors but the car was idling perfectly fine and upon warm restart fouled the plug just about instantly. When I start the car tomorrow I'll put the other plugs back in and play with the settings a bit to see if I can eliminate this. VE analyzer works great as long as you go back through and smooth stuff out afterward! Link to comment Share on other sites More sharing options...
importwarrior Posted September 24, 2015 Report Share Posted September 24, 2015 some plugs stick too far in to the chamber but i thought the 7031 were what the car came with new? Link to comment Share on other sites More sharing options...
polarisman14 Posted September 24, 2015 Author Report Share Posted September 24, 2015 Not sure but I am running the 5534s right now (I think)--BPR7ES. BPR8s were what was in there to begin with in my case. If they are sticking too far into the chamber would that have anything to do with fouling the plug? Additionally, I changed from 3.1.1 firmware to 3.4.0 and of course there are differences...Why the hell doesn't someone just make a patch that automatically converts old tune files to updated firmware signatures without losing any of the settings? Seems silly that it doesn't just do that by itself. Link to comment Share on other sites More sharing options...
speedyquest Posted September 24, 2015 Report Share Posted September 24, 2015 Sometimes its just not that simple software wise. Link to comment Share on other sites More sharing options...
polarisman14 Posted September 24, 2015 Author Report Share Posted September 24, 2015 Yeah, that's when you wait longer to release the firmware lol. Oh well. I'm sure playing catch-up isn't too involved as it tells you what fields are affected--problem is there are 67 of them in my case! I have a buddy helping out with my tune and I am hoping he can suggest a work-around for it other than taking all the constants etc and dumping them into a clean slate/project. Link to comment Share on other sites More sharing options...
speedyquest Posted September 24, 2015 Report Share Posted September 24, 2015 (edited) Well they don't make a "patch" to convert old formats because if they are changing quite often it would take a ton of time to make a tool each time they did that. But that being said it isn't smart for them to be changing formats often, they will create issues for their customers (you) and complicate the work flow of your software exponentially when it comes to people trying to upgrade. EDIT: Reading your other post again I noticed you mentioned signatures. Is that just a signing of a document to verify it is a file it can read or did they actually change the file layout / formatting of the files? Edited September 24, 2015 by speedyquest Link to comment Share on other sites More sharing options...
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