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DFI and ECMDiscuss all aspects of DFI (Digital Fuel Injection), ECMs (Electronic Control Module), scanners, and diagnostic equipment. Fine tune your Third Gen computer system for top performance.
I'm curious if anyone has ever seen anything like this peak I have in my VE table or even ever seen one this big:
(This is still a work in progress, but it's pretty well tuned below 3200rpm above there it needs a lot of tuning)
That hump in the VE seems to correspond to a spike in cylinder pressure since I had to pull timing way back in that area to keep the knock retard down to something controlable- like this if I load it down in 5th gear basically standing on the brakes and gas at like 80mph it's OK for a second or 2 and then typically I start getting some knock that takes 4* retard to get rid of):
I'm thinking of dropping some cooler plugs in it just to see if that lets me run some reasonable timing in that range but I don't really expect it to.
The combination:
stock 305 bottom end, LT1 aluminum heads converted to work on SBC (with a bunch of port and chamber cleanup), about 8.4:1 compression, Victor Jr intake converted to FI, fabricated elbow to an LSx style throttle body. The cam is {edited for the sake of the discussion, I'll try to remember to put it back later or if someone reminds me}
It's running a Megasquirt 2/PCB 3.0 with MSExtra firmware
Last edited by 83 Crossfire TA; 10-08-2016 at 04:23 PM.
You arent suppose to lug a motor that hard at that low rpm. I havent seen a ve spike like that and would say that does not seem normal at all.
That's the thing, i'm not lugging the engine, it's perfectly happy, not making any lugging or jerking noises or actions... I know it's crazy but it's a lot like driving my cummins dodge below 1500rpm, and the stock TPI top end/cam didn't have a chance in doing this like this (I'm assuming that you're talking about the video).
That said I mostly did that for the video, I don't often drive around under 1200rpm, but it the way it's geared cruise is typically a happy 1200-1800rpm
Wot at max rpm should be higher value unless some other enrichment table is adding on top of that table
{edited for the sake of the discussion, I'll try to remember to put it back later or if someone reminds me}
FWIW, this car has 800cc/72# ev14 injectors in it, and I have wondered if some of that is the big injectors going non-linear down there. I'm at pulse widths of 1.5-1.7ms around idle which should put me a little above the non-linear range and I have tinkered with a few things to eliminate that and any harmonics from the length of the vacuum line to the FPR and other plumbing issues. That and I wouldn't expect it to happen at the same rpm independent of load.
Last edited by 83 Crossfire TA; 10-08-2016 at 04:22 PM.
Even in first gear after being tuned in first?
Is this in NORMAL WOT or are you inducing extra load?
Vanilla, you have me a bit lost with this and the last question.
If you were asking about the video posted above it was shot in 5th gear.
If you're asking how i tuned in the VE around 1600-2000rpm at high MAP values, then originally I was inducing a load, it would be in 3rd or 4th (5th puts it around 85-90mph), and I would stand on the brakes and throttle till I got it to hold that load in whatever gear I was in (and it made for some REALLY crispy brakes). This was most of the tuning before I posted this.
More recently I did find a stretch on a divided highway that had 2 big hills where I could shift it into 5th and give it throttle till I got it in that range and the hills were steep enough that i could get 5-10 seconds under load in that range (typically I'd start around 1300rpm and if I was careful I could get it in that range for almost 10s by about 2200rpm. Doing it like that I found that I needed slightly MORE fuel in that area but it was less detonation sensitive- loading it like this I don't typically see any knock retard for 4-7s before it kicks in.
I also swapped in some autolite 103's for the NGK TR55's that were in there (the TR55's are the stock LT1 plug, which I figured would be a little cool on a 305, a TR6 is one heat range cooler and roughly cross references to a autolite 103). This is what the NGK's came out looking like, no aluminum bits or oil fouling, which is sort of the only thing that you can _really_ read off of street driven plugs, but I'm pretty sure I got them pretty carboned up at some point and burned it off, they might be a little hot. I doubt that the NGK's had much more than 1000miles on them (a few tanks of gas, I'm getting about 250miles out of a tank). FWIW, the cooler plugs run smoother and the datalogs are less noisy with them, but the VE table didn't change and the Knock didn't go away.
Yeah, that's exactly why i am asking. You are tuning for a situation you should have never been in.
If you drive a turbo car like that you will blow the motor.
Don't force high load at low Rpms unless you are in the right gear to do so.
There is ONLY one way to fix this and that's to STOP driving like that. Shift to a proper gear with that much throttle.
Edit: I also want to add that per gear timing and fueling, or altering valve events can help this too via variable valve timing changes or cam swap but the cause is still improper gear choice and artificial load.
Last edited by Vanilla Ice; 09-23-2016 at 01:50 AM.
I also dont think that package is a 7000 rpm 460 hp deal but certainly should be a fun 305
Honestly I have a hard time believing what I'm seeing with it. I expected it to want to turn up to too high an rpm (every simulation that I got the combination close to with my head flow numbers and cam timing showed a torque peak of 4000-4400rpm and a hp peak at 6800-7400rpm and I swore I wouldn't turn it over 6800 even it it wanted to go that high), but if you didn't know, didn't open the hood and just started it up and heard it idle you'd just think it was still stock with a loud muffler on it (it idles smooth but it got noticeably louder than when it had the stock top end on it). It actually pulls harder than the TPI did EVERYWHERE, from 700rpm up, the low end this thing has would be beautiful in a truck, but I can't get it to idle consistently below about 600rpm.
I made a few runs last night up to the mid 6K rpm range in 2nd and 3rd gear, It was hazing the 305 drag radials at the top of 2nd gear, and I never got over 73% throttle and 95KPa (most of it was around 90KPa and when I first hit it TPS% got in to the 80's before I chickened out trying to keep it on the road, **** just happens too fast up there for where I was). Besides where AE kicked in it was at between 13.7 and 16.1AFR everywhere above 5000rpm. I'm guessing I need a ballpark of 5% more fuel everywhere up there. It's also hard to tell because it went lean but I saw quite a bit of knock retard up there, right now it looks a lot like it might only want something in the high 20's for SA up there (which I find pretty weird for an SBC, but what the heck, the rest of this is pretty weird)
Stop running this through multiple threads and read the responses.
Originally Posted by Vanilla Ice
Yeah, that's exactly why i am asking. You are tuning for a situation you should have never been in.
If you drive a turbo car like that you will blow the motor.
Don't force high load at low Rpms unless you are in the right gear to do so.
There is ONLY one way to fix this and that's to STOP driving like that. Shift to a proper gear with that much throttle.
Edit: I also want to add that per gear timing and fueling, or altering valve events can help this too via variable valve timing changes or cam swap but the cause is still improper gear choice and artificial load.
What do you mean running this though multiple threads? This is the only place I've posted about this, I may have started the conversation in the swapping LT1 heads conversation but I started a new thread here because it's a different conversation.
Listen to what? You haven't said anything but "stop driving like that" in this post. That would be useful if I was talking about driving like in that video AND THEN loading it down, but I'm not (and if you think I am YOU should read what I wrote actually wrote and stop telling me to read replies).
AGAIN, This crazy peak is at 1800rpm (and I have columns at 1800 and 2000 to try get the tune dialed in which are pretty high also). That's 5th gear cruise on the highway (about 60-75mph), and under the "right" conditions it takes >30% TPS to drop the MAP into the 90-100KPA range.
That is not an artificial situation, it's hitting a hill on the highway or speeding up a little to get around someone. Driving around partially loaded at 1800rpm in a V8 powered car is normal, heck, it's not uncommon to hit this kind of load in a v8 powered car at 1300rpm with an automatic, and I have no issues with that below 1600rpm. i did initially test it by loading it with the brakes in that range, but I've found 2 hills on a divided highway, going both 2 and from the gym that I hit this range for a few seconds EVERY time (the funny thing for this conversation is that my 2012 SHO, twin turbo + automatic hits almost exactly the same RPM and is under boost on those hills)
The video was shot well before I knew there was something up in the 1600-2000rpm range, and the point in posting it is that it runs fine below that with no knock or anything else. If this was about rolling into the throttle
Couple more things I can add for you.
You can't compare ANY car to your car. You've made it not like low RPMs and are trying to force it to. And EVERY SINGLE CAR is different. Different gears, different rear ends, different intakes, cams, heads, VEs, timing tables, different engines, different transmissions, different turn signals, different oil fill caps, different coefficient of drag. Do you see where I'm going with this? You can't compare other cars abilities to this one.
ANY automatic WILL NOT drive how you are driving. They can unlock the converter, or shift which you can't do. WHICH IS A HUGE difference. Not to mention what I just said above.
5th gear is overdrive. Overdrive is not a passing gear. It's not a hill climbing gear. It's not a high throttle gear. It's not a force poor driving habits on your unhappy motor gear. It's a low RPM CRUISING gear. Cruising is NOT high load. Cruising is NOT climbing hills. Cruising is NOT passing people.
If you want the car to like higher VE at lower RPM change your cam first. Otherwise give it the RPM it needs to survive and do what you need.
Couple more things I can add for you.
You can't compare ANY car to your car. You've made it not like low RPMs and are trying to force it to. And EVERY SINGLE CAR is different. Different gears, different rear ends, different intakes, cams, heads, VEs, timing tables, different engines, different transmissions, different turn signals, different oil fill caps, different coefficient of drag. Do you see where I'm going with this? You can't compare other cars abilities to this one.
I've made it not like low rpms? How's that? It doesn't lug with a reasonably load from idle (which is an artificial situation), but it does have spot that seems to want A LOT of fuel at 1800rpm. I guess 1800rpm is "low rpm" for a power curve, but not so much for cruise compared to some stock engines from that vintage and relatively low compression.
ANY automatic WILL NOT drive how you are driving. They can unlock the converter, or shift which you can't do. WHICH IS A HUGE difference. Not to mention what I just said above.
5th gear is overdrive. Overdrive is not a passing gear. It's not a hill climbing gear. It's not a high throttle gear. It's not a force poor driving habits on your unhappy motor gear. It's a low RPM CRUISING gear. Cruising is NOT high load. Cruising is NOT climbing hills. Cruising is NOT passing people
That's just plain wrong. There are loads of similar combinations that will keep the auto in high gear with a locked converter that will stay that way at 25-30% TPS, and that's what it takes to get in that load range.
GM actually forced similar loads on the LT1 and LS1 f-bodies through their skip shift algorithms (forcing 1-4 shifts under conditions where you were not accelerating hard).
If you want the car to like higher VE at lower RPM change your cam first. Otherwise give it the RPM it needs to survive and do what you need.
OK, I'd love to hear this. It's an 8.4:1 compression 305, you know it's backed up by a stick shift and relatively tall effective gear ratio. Give me a ballpark what cam you'd expect in this, a ballpark what powerband you think I'll see from that....
I've made it not like low rpms? How's that? It doesn't lug with a reasonably load from idle (which is an artificial situation), but it does have spot that seems to want A LOT of fuel at 1800rpm. I guess 1800rpm is "low rpm" for a power curve, but not so much for cruise compared to some stock engines from that vintage and relatively low compression.
That's just plain wrong. There are loads of similar combinations that will keep the auto in high gear with a locked converter that will stay that way at 25-30% TPS, and that's what it takes to get in that load range.
GM actually forced similar loads on the LT1 and LS1 f-bodies through their skip shift algorithms (forcing 1-4 shifts under conditions where you were not accelerating hard).
OK, I'd love to hear this. It's an 8.4:1 compression 305, you know it's backed up by a stick shift and relatively tall effective gear ratio. Give me a ballpark what cam you'd expect in this, a ballpark what powerband you think I'll see from that....
My auto ls1 and 6 spd auto 6.2 truck will not stay in high gear in those positions
A milder cam in the 206-212 deg range on a tight lsa may do better in that position
Did you drive other spots yet to see what the ve table wants at other rpms and loads around that spot
My auto ls1 and 6 spd auto 6.2 truck will not stay in high gear in those positions
A milder cam in the 206-212 deg range on a tight lsa may do better in that position
Huh, I'm not sure I get where you're going with that, shorter duration = shorter power band, more low end, tighter LSA = more midrange less at the bottom and top (yes, way oversimplified). My initial thoughts are that something like a 212/212/108-110 would be the same or worse in that range, and lets say 206/206/106 would be similar, worse to tune for EFI and both would be totally inappropriate for a turbo motor (again, this is a low compression setup that I'm building to turbocharge).
When it comes down to it the current 218/218/112 isn't all that different then the range that you suggest, and should be similar to something like a 228/228/112 in a 350.
The fact is that I shouldn't be seeing a HP peak at somewhere north of 6800rpm and I shouldn't be seeing a ve peak (torque peak???) at 1800rpm with those cam numbers. Well not exactly, i expected the HP peak to be past what I was willing to rev it to based on what I did to the heads.
It would have been nice to tighten up the LSA to limit the top end some. Honestly, I considered something like a 212/212/110, but Tim Cole was positive that I would think that even this cam was too small for what I wanted, but now based on how this is acting something like these lobes on 108 or 224/224/110 (or even 108) would be interesting in this thing, but again not appropriate for a turbo.
Tim was pushing for 224 or even 230 from the same lobe series with a 114LSA. I couldn't imagine what the top end would be like with 6-12* more duration and more lobe separation. I already have WAY more rpm capability than I dare to use...
Did you drive other spots yet to see what the ve table wants at other rpms and loads around that spot
Yea, at this point I have pretty much everything under about 6500rpm tuned in pretty well (well fuel wise, SA not so much since i'm still chasing some knock retard that isn't reacting as expected to SA changes). I'm very close to my AFR targets and when I turn the EGO correction back on I almost never see more than 2-3% correction anywhere. The fuel table looks very similar now to what it did, basically the same shape, still the crazy peak at 1800rpm:
09-16-2016, 01:22 PM
