Drax240z Posted November 2, 2003 Share Posted November 2, 2003 The title pretty much sums it up. I'm converting to larger injectors on my sds, and I'm curious how to reporgram using my current map, rather than starting from scratch. I would suspect that if I am converting from 260cc to 440cc injectors, then I can basically divide current values by 1.7 for a few things. The question is, do I divide everything by that change? RPM fuel, start, map fuel, etc? Or is there a better technique? Quote Link to comment Share on other sites More sharing options...
Drax240z Posted November 3, 2003 Author Share Posted November 3, 2003 *Bump* I know a couple of you have done this... Doug? Scottie? Bueller...? Quote Link to comment Share on other sites More sharing options...
Ron240zxt Posted November 3, 2003 Share Posted November 3, 2003 Hello, What size injectors do you have now, and at what fuel pressure (static) do you run? Also have you checked out the forum on the sdsefi site. I believe Mandy posted this before, If i can recall. I'll try to help out as much as possible. Im currently running 550cc injectors myself. Quote Link to comment Share on other sites More sharing options...
Scottie-GNZ Posted November 3, 2003 Share Posted November 3, 2003 I was waiting to give someone else a chance to jump in and relay their experience. All SDS fuel programming anchors off the base number derived from a combination of the cylinder displacement and the inj flow rate. The trick is how to maintain the fuel curve after generating the new base number. Here is my trick: Create a spreadsheet that has 3 columns: RPM, Fuel Value, % Increase. Put the RPM increments in the 1st, the fuel value for the corresponding RPM in the 2nd and a calculated % increase for each increment in the 3rd. Next, add a 4th column for the new fuel value and go to the matrix below and figure out your new base number. Put the new base number in the cell that represents 500 RPMs for your 4th column. Next, write a formula in the cell below that one that will increase the base number by the % increase in column 3, then copy that formula in all subsequent cells in the 4th column. You have now generated the same fuel curve using the new base. The new values will definitely have fractions, so round accordingly. Of course, if you are unfamiliar with spreadsheets, then what I just said probably means nothing Couple of things to keep in mind. Build the RPM FUEL curve to match the torque curve not the HP curve. That means your values should basically stop increasing after 5000 RPMs. DO not use the RPM FUEL map to compenstae for lack of fuel under boost. If you do, you will also have that extra fuel when not under boost. The numbers are not cast in stone so further fine tuning will be required. I have never been able to get a L28ET to idle correctly with the base number so play around with the number to get it to idle correct but still use that number as the anchor for off-idle and above. I suspect most of the time the idle problem is air leaks wanting it to idle richer. HTH, Quote Link to comment Share on other sites More sharing options...
Drax240z Posted November 3, 2003 Author Share Posted November 3, 2003 Like I said in the first post (though it wasn't terribly clear) I am going from 260cc/min to 440cc/min injectors. Running stock fuel pressure. Spreadsheets... yeah I've seen one before I think. I followed your description though it's a bit easier for me to visualize as a fuel curve, and basically keeping the same first derivative throughout the values on the fuel curve, even with the larger injectors. Ya, ya, silly engineers. So Scottie, if I am following you right then you are only reducing the RPM FUEL values to compensate for the larger injectors... I guess regardless I am just going to have to try it and see. I would think the MAP FUEL values will also need to be reduced... no? And START, and TEMP... I guess its sortof back to square 1, though I guess I know the shape of the curve that works for me for MAP FUEL so I could continue with that shape as well. On a side note, I removed my muffler a couple days ago and picked up gobs more power... Combined with the near freezing temps here, and the dry roads, things are fun. Quote Link to comment Share on other sites More sharing options...
PETEW Posted November 4, 2003 Share Posted November 4, 2003 When I bought my SDS I told them I had 370cc injectors (SVO). Does that mean the basic map that they put in is based of that injector size? I would assume so. I am very intersted in this post since I have a feeling that I will have to move up to 440cc injectors when I put in a hybrid turbo and run big boost. I am so glad there are guys like Scottie to help out. Quote Link to comment Share on other sites More sharing options...
Scottie-GNZ Posted November 4, 2003 Share Posted November 4, 2003 Hope I did not muddy the waters and since pictures tell a story better, here is what the spreadsheet would like and the corresponding graph showing the fuel curves. Do not take these numbers as gospel!!! I just quickly put this together as an example. In the spreadsheet you see RPM and Fuel values that would be programmed in the RPM FUEL map. In the 3rd column you see the % increase for each increment. The value of 122 was derived from the table above based on 290cc injs and 466cc cylinder displacement. Everything else anchors off that number. Note that there are no dramatic increases in fuel in this map as it is strictly for "normal" driving. I never used the TPS and would add just a little extra at the off-idle point for a crisper response. If you use the TPS, the SDS will handle that for you. Remember the TPS is only used to trigger a little extra fuel for off-idle (at least in the model I used). The SDS compensates for increasing RPMs and that is why this table looks so flat. Do not make big incremental jumps. In the 4th column I used an anchor number of 82 based on 466cc cylinder displacement and 440cc injs. I then applied the % increase number in the 3rd column to the anchor number in column 4 and let it generate new numbers for the map and round off those number. Next to the spreadsheet is the resulting maps visually and they are identical. Every other fuel map, be it for boost, cold start, etc, is also anchored off RPM FUEL. IOW, "add fuel to RPM FUEL to compensate for boost, cold start, etc.." So, do not change those other numbers initially if you change injs. Get the car to idle smoothly, have crisp off-idle and accelerate normally w/o boost by tuning RPM FUEL. Once you get that right, then program the others as needed. Quote Link to comment Share on other sites More sharing options...
Drax240z Posted November 4, 2003 Author Share Posted November 4, 2003 Wow, now that is a comprehensive reply. Thank you very much Scottie! Can I ASSume that the shape of your RPM FUEL curve shown here is similar to what you were running? The reason I ask, is I have gotten someone conflicting stories on how to set it. I realize that you should have RPM FUEL the highest at the torque peak. Mine looks something like this: 500 100 750 100 1000 100 1250 105 1500 110 1750 115 2000 120 2250 125 2500 130 2750 135 3000 140 3250 145 3500 145 3750 145 4000 145 4250 145 4500 145 4750 145 5000 145 5250 145 5500 145 5750 145 6000 145 6250 145 Which seems quite a bit more abrupt and varied than what others are doing. I'm going to tinker a bit more, but perhaps increments of 5 are too much. SDS suggests you find your injector value, and -10% at low rpm, +10% at high rpm or something like that. (its escapes me at the moment) I pretty much followed their instructions, adding in a somewhat smooth transition. Comments welcome. Quote Link to comment Share on other sites More sharing options...
Scottie-GNZ Posted November 6, 2003 Share Posted November 6, 2003 Sorry, I hate it when work gets in the way Those are not the numbers I used and were not intended to be presented as numbers anyone should use. I have not had to do any serious tuning on the SDS since I switched and that was almost 4yrs ago! I am just trying to help folks understand the basic principles and if SDS has new information about programming (the bit about -10% and +10% is new to me) then follow it applying the basic principles. I think Z-Gad can attest to how nice it is once you understand the basic principles and be able to understand what change is required and what effect it will have on the overall tuneup. He can also attest to the negative effects of having large and not smooth increments. BTW, great thread and the kind that goes a long way in helping everyone tune. There is no magic map everyone can use and there is no out-of-box map that will come from SDS specific to your setup. There are just too many variables to make that possible. However, if everyone understands the basic principles, they they will know what tweaks to make to baseline maps for squeezing out the last ounce of power. In most cases there is as much power to be gained from serious tuning as from going to bigger parts, but that requires thinking and patience. Quote Link to comment Share on other sites More sharing options...
Drax240z Posted November 6, 2003 Author Share Posted November 6, 2003 OK, well I've been playing some more. Not that the car was running badly on the old map I was using, but you know... gotta tinker. I found out that transitions of ~8 or more between RPM FUEL vales tended to make the car cough and sputter a bit between transitions. SDS's suggestion is to find an injector value based on 1 cylinders displacement (466cc) and your injector flow rate. (260cc) On one of their web pages they have a graph... you need to do a dual linear interpolation to get the exact vales. From there you should punch in your exact values (mine works out to 131 for RPM FUEL) into the SDS, -20% at low RPM, +20% at high RPM. This is SDS's suggestion for a base. It didn't work out that well for me. I found it was too rich at idle and too lean on the top end... Right now I am running something like: 500 095 750 098 1000 103 1250 108 1500 113 1750 119 2000 124 2250 129 2500 133 2750 137 3000 137 3250 137 3500 137 3750 137 4000 137 4250 137 4500 137 4750 137 5000 137 5250 137 5500 137 5750 137 6000 137 6250 137 Seems to be not too bad. I still pretty much have the mixture meter pegged at full rich. (narrow band, unheated) I'm relying on closed loop mode to give me decent fuel economy, and right now its pretty much pig rich everywhere else. Query: Thoughts as to whether a EGT/narrowband combo would be better than just a wideband? I'm pondering that now... Quote Link to comment Share on other sites More sharing options...
Doug71zt Posted November 12, 2003 Share Posted November 12, 2003 Sorry Drax - Can't offer a lot of help here right now - I'm in Manila and all my Zcar stuff is in Ontario. I can't offer any comprehensive advice because I changed so many variables at once on my engine (550cc injectors, turbo, fuel pressure reg, fuel pump, rail, IC, piping, exhaust and SDS version update) I had to start from scratch with the whole fuel curve. Good thing we have Scottie as a resource.....My Z is up for the winter now - same thing next spring (ported head, ISKY cam, ss valves, 3.0L bottom end with 8.3 CR.) And a better tranny Good luck - Doug Quote Link to comment Share on other sites More sharing options...
Drax240z Posted November 12, 2003 Author Share Posted November 12, 2003 Well I am getting somewhere for sure. Unfortunately it has been a bit damp here lately, and traction is NIL. The car is very quick, but not in the wet. It just makes a lot of noise and goes sideways in the wet. I think my values are pretty good now for the stock injectors. (though 137 is a little high still... but I'm erring on the rich side) Now that I've got that figured out I am going to pull the car off the road and do a bunch of changes. Finally my 440cc/min injectors, polished intake, walbro pump, etc are going to go in the car. I figure I'll pretty safely be able to run 15psi at that point. (right now I am running ~12psi) I have the middle size NPR to put in (from the small one) as well. One way or another I am going to compete in autocrosses with this car and engine. (coilovers, vented brakes, 5 bolt conversion, roll cage are also going in this winter) Gotta find me a wideband... Quote Link to comment Share on other sites More sharing options...
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