XFI Tuning on a 383 Turbo Motor

[Fastbird]

Figured since the wrench work is primarily done, I'd start a thread about the tuning process with the XFI so some people can hopefully learn some of my knowledge and I can hopefully learn from other peoples knowledge.

The XFI comes with a myriad of "starter" tunes in it. When I first started my car, I used a baseline 383 tune that was set for 30# injectors. Car cranked right up. Second go though, I switched to a 355 Turbo tune with 160# injectors because it was set for a 3Bar map so the scaling on the graphs was correct. Obviously I changed the necessary constants like injector flow rate, crank reference signal, ect.

So, On the 355 tune, I had to scale the VE table WAY back.........the extra cubes and the 85 lb injectors at a .8 bpw was making it rich everywhere. I managed to drive it around the block a couple of times but it was backfiring on tip in, presumably because of the AE vs. TPS Rate table in the XFI which is the auto enrichment. The 355 tune appears to have been geared towards a race car setup so it's on the slightly aggressive side. The XFI makes it VERY easy to do your tuning because of the Wide band that's integrated to the system......and it had a neat feature where if you're operating in a cell adn it's in closed loop, pressing the L key will auto correct the cell for the amount that the correction is happening. I haven't gotten too in depth with it because of time and frustrations yesterday, but I'll be updating this thread as I continue the tuning process.

Now, there's an issue that presented itself to me. After the car had been running for a while, it started acting weird. Weird as in there was a sudden and random noticeable drop in popwer, it barely responded to throttle input, and the idle started dropping down low for no reason, and no matter how far I tried to crack the blades open, it would still find it's way lower than where I had it set. Any thoughts on this?

[BLK WS6]

I have only briefly had the pleasure to tune with XFI...its pricey but i agree very user friendly. The real time tuning is nice! Which mode are you using? I can't recall the names off the top of my head (speed density and have hybrids of maf/speed density) but I know that will effect your closed loop tuning.

[Fastbird]

There's Sequential, Speed Density, and Alpha-N. Alpha-N is the least precise of the three and apparently isn't utilized very often, typically on VERY low vacuum engines. Sequential requires the use of a crank sensor, which takes my motor out of the picture. I'm using Speed Density in batch fire mode obviously.

Found the issue from Saturday. Fuel Pressure. Working on that. The in-tank lines from the pumps to the y-assembly went to mush. Hopefully I'll get it running again this evening and see if the wide band is working.

Something about the XFI that bothers me is the scaling of the graphs. There's only a certain amount of lines on the graph, and you ahve to fit the operational parameters into that section. Case in point, I have the X Axis on the main graphs (RPM) set to 800, 1200, 1600, 2000, 2400, 2800, 3200, 3600, 4000, 4400, 4800, 5200, 5600, 6000, 6400, and 6800. The Y Axis (MAP) is set to a differing rating up to 312 kPa for the 3Bar map sensor. I don't like that if you want to fine tune one area, you need to scale it closer, but then you ahve to widen the spread in the rest of the graph. For Instance, if I wanted to REALLY dial in my off boost tuning, I'd set the graph to be 800, 1000, 1200, 1400, 1600, 1800, 2000, 2200, 2400, 2600, then 3000, 3800, 4600, 5400, 6200, 7000. So I get a nice close area to work with down low, but then have a wide spread for the upper RPM ranges where accurate fueling becomes more critical.

*Disclaimer* -- The XFI does have an interpolate feature, where you can highlight the cells in the graph, then command it to interpolate. What it does there is basically smooths out the 3D graph to create a nice smooth curve to everything rather than large jumps at the predetermined cell points.

What I'll probably end up doing is just keeping the 400 RPM spreads because I can't see the motor wanting or needing to spin past 6800 RPM. It may make it a little chunky down low but I'll be safer up high when I'm in boost and such.

[Tony Shepherd]

Actually it does have the interpolate function Sean. I use it.

[Tony Shepherd]

Also what some do about the scaling of the graph limitation is make two tunes. One for streetability in which you scale more in the drivability range, and then another tune you scale more for WOT.

[Fastbird]

Actually it does have the interpolate function Sean. I use it.

Also what some do about the scaling of the graph limitation is make two tunes. One for streetability in which you scale more in the drivability range, and then another tune you scale more for WOT.

I wrote that funky. What I was saying is that it DOES have the interpolate feature, just that if you evenly spread things it's interpolating a rather large gap.

The two tune idea isn't that bad....but given my tenacity when out driving I'm probably better off to sticking with a single tune that has a broad even coverage. :D Get myself into less mechanical trouble that way.....

[Fastbird]

Ok, tonight make a couple of around the block passes. Had to really richen everything up from idle up to 3200 where I've got the limiter set at. Response was sluggish and chuggy and any kind of throttle movement caused a nasty backfire......so I figure there's too much timing. Pull timing out and sure enough, response gets MUCH better and the backfire goes away for the most part. Still a bit of backfiring at low throttle on initial TPS Movement, but I should be able to work that out.

One thing I'm finding is that the 1/4" bleed hole I have in the TB just isn't enough. Set the idle when warm, cold start it barely idles at 800 RPM on a commanded 1100. Open it up, once the car warms up, I'm idling at 1100-1150. I am hesitant to drill a larger bleed hole in the TB but am finding that I may have to.

Here's a question for the tuning types. This cam likes timing at idle to keep the vacuum up. I've got 30 to 32 degrees in at idle. What can I do to keep it from going turd like when I tip in the throttle and dump 8-10* of timing right off the bat.

*Admission* Timing is my weak point. I've never played with a blank timing table before, only modded an already running setup. So this is all kind of new to me there, and if anyone has any advice, I'd LOVE to take some.

[BLK WS6]

I have never drilled a breather hole in a tb...I always just adjust the tb blades/tps until the IAC counts are kosher. You should try to have a nice smooth transition for your timing also...even if you increase or decrease by large increments.

[Fastbird]

Well, the stock TB has a IAC Bleed hole in it, and I'm trying to keep things as factory as possible because I can't monitor each side independently as it's set up. So if I was to use the blades to get idle air, then I'd potentially run into uneven airflow and fueling left to right.

I know the timing should have a nice smooth transition, and from what I've gathered timing should taper off as RPM increases and as MAP increases, so you get a graph that's a downhill slope on the X and Y axis alike. I'm just trying to figure out if that's truly correct, that the highest timing should be at the lowest point because with my car it seemed like with more timing it had a greater tendency to backfire on me. I had to pull it back into the low 20's in the 1000-2000 range at MAP ranges from about 20 to 100. I did get the car idling at about 68-70 KPA at best, with about 30 to 32* of timing set in at idle cells........but at 1400 RPM it dumps like 8*........I probably just need to tweak on it some more.

FYI, right now I'm only trying to tune in the 0-3600 RPM range and the 0-100 KPA MAP range...just for the off boost driving to break in the motor.

[Ryan Stout]

Can you use the stock gauges or did you keep your stock ECU and use it for gauges only?

[Tony Shepherd]

Sean, email me your timing table

fast93z@gmail.com

[Fastbird]

Can you use the stock gauges or did you keep your stock ECU and use it for gauges only?

Still using my stock gauges. The Fast Track harness kept everything working. I'm VERY pleased with that.


Sean, email me your timing table

fast93z@gmail.com

Tony, I'll shoot it over to you when I get home tonight. Do you want the entire .gct file or just a screen capture of the timing table? Thanks for helping out!!

[Tony Shepherd]

Still using my stock gauges. The Fast Track harness kept everything working. I'm VERY pleased with that.



Tony, I'll shoot it over to you when I get home tonight. Do you want the entire .gct file or just a screen capture of the timing table? Thanks for helping out!!

You can send the whole gct file if you want. I will look at it and I may send it to Moe and see if he will look at it as well.

[Fastbird]

That would be awesome Tony. Email coming your way shortly.

[Tony Shepherd]

Email sent

[Fastbird]

Ugh.....this thing is kicking my tail. I remapped the vertical axis on the graph, which really made no big deal because I moved the numbers around close to what they were and should be. Then I bumped the base pulse width on the injectors from a .8 to a 1.0 as FAST recommends leaving it at, knowing that was going to make me rich all over the place. No biggie. I can work that out.

What I can't get it to stop doing is damn backfiring out the exhaust whenever I move the damn car around. The ONLY way I can get it to stop that is to severely retard the timing back into the 20 and below range. It doesn't show up on any logs, but I'll be damned if I give it just a little bit of throttle and try moving it that it backfires through the exhaust. If I kind of stab it and get more aggressive it doesn't backfire, but if I try to be nice and just drive like a normal person, constant popping and backfiring through the exhaust. It's NOT doing it through the intake, that much I can tell.

And I hope the smokeshow clears up soon.......it's still pumping quite a bit out. :(

[Speed Density]

Why dont you just get a tuner or take it to a tuner, Sean?

[Fastbird]

Stubbornness. And money.

[Speed Density]

Ok, makes sense.

[CALL911]

Do you have the full exhaust on? Or are you just running around with the headers and Y-pipe?

I remember when I initially installed my 383 (from my original destroyed factory LT1) and started it up just with the headers on, and it was doing the same thing until I put the rest of the exhaust on.

[Fastbird]

Ben....its had a complete exhaust done before I tried to start tuning it. This looks to be a situation where I'm simply in over my head.

[CALL911]

^ Every tuner had to start somewhere.

Unfortunatly as complicated and as vast as your speed density, FI, LT1 FAST setup is, it may in the end take an actual tuner to get you dialed in. Which = money, which in turn for you will = more time :(

[Tony Shepherd]

Sean I just talked to Moe. He wants to help out. He willl be contacting you.

[MoeHorsePower]

Hey Sean, send me your tune so I can look at it if possible. You still running an Opti? Fill out the following. PM me if you want.

ENGINE SPEC SHEET
Name: Phone #:
1. Year:__________
2. Make:_________
3. Model:________
4. OBD1___ Or OBD11__
5. Engine Size:________
6. Compression:________
7. Stock Heads___ Ported_____Flow #:_______________
8. Injectors: Stock:___ / Other___
9. Brand Injector:____________. Size:________
10. Fuel Pressure: Stock:___/No, What Pressure:_______
11. MAF: Stock:__/No__Other:______/ Size________
12.Throttle Body:Stock__/Other:_________/Size_______
13.Cam Specs:Duration:__________/Lift________/LSA___
14.Fuel Pump:Stock:Yes:__/No:__/Brand&Size:________
15.Trans:M6:_/A4:_./Stall_____./Shift Kit:Yes:___/No:___
16. Rear Gear:__________/Tire Size:____________
17. N/A: Yes:___/No:___/
18.Forced Induction:Yes:__/No:__SuperCharger:__/Turbo:__
18. Boost Lbs:_____
19.Nitrous Shot Amount:_____
20.Timing Retard Box:Yes:___/No:___

[Fastbird]

Email coming your way Moe. Thanks for looking at this!