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vehicular thaumaturgist
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AdamVR4 said:
Chris, they won't be. I really think ~660's are the perfect size injector...
I'm hopin', but keep in mind that I want comparatively lean A/Fs most of the time (not much below 12.0:1) and plan on using water/alky at some point. I guess we'll see.
 

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I went from 550's to 720's and didn't look back. I didn't like the way the car performed above 20psi with the 550's. There wasn't enough timing advance once the IDC's started climbing. I was getting little gains going from 18psi - 22psi; just higher EGT's. When I swapped out the 550's for 720's, even on a semi-rough tune, the car felt completely different. I regularly run 16-17psi on pump gas and have never had any issues with timing-induced knock. I also never had any driveability issues - my car starts, idles and drives damn near stock. In fact, for some odd reason, I've found my 720's easier to tune than the 550's (both Denso).

I completely agree with the core subject of the initial post. However, there is merit to intentionally overkilling on injectors to boost the timing a little. Although, I wouldn't recommend it for those with knock-prone stock heads.
 

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Multiades said:
I'm hopin', but keep in mind that I want comparatively lean A/Fs most of the time (not much below 12.0:1) and plan on using water/alky at some point. I guess we'll see.

I ran lean as hell all the time. I tuned for 11.7:1 on the dyno and it NEVER got richer than that ever again. :)
 

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HellBringer said:
Although, I wouldn't recommend it for those with knock-prone stock heads.
Or, more importantly, worn, original valve stem seals. ;)
 

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Velocity Algorithms
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Igottabumpit.
 

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SMTCapeCod said:
Crap, the first paragraphs (Thanks Trevor) make me think that going with 510cc to support my 13G upgrade wasn't too bright. However, right now with my 9bs I'm only seeing 86% avg IDC. Guess I'll have to do some WOT runs and log the results-- I'm just learning to correlate the different log functions with the engine characteristics they can help diagnose. Posts like this really help.
I'm currently running 510cc injectors with 13G's. I definately think going any bigger, like up to 550cc would've been stupid. As it is, I've never seen my IDC's go higher than around high 80's @ 15psi, and thats when I'm really punching it. I guess I probably could've gotten away with 450cc injectors, but I don't see it making much difference at this point.

I definately have no complaints performance-wise though. My car feels great with that setup.
 

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bjmsam said:
O2v Front = .90 V
O2v Rear = .92 V
Knock Count = 0
RPMs = 6844
TPS = 96%
IDC = 122%
Timing = 22 Deg
450cc injectors would seem barely adequate for my 9Bs:
122% IDC * (360cc / 450cc) = 98% IDC
122% IDC * (360cc / 550cc) = 80% IDC

What am I doing wrong, here?

 

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bjmsam said:
450cc injectors would seem barely adequate for my 9Bs:
122% IDC * (360cc / 450cc) = 98% IDC
122% IDC * (360cc / 550cc) = 80% IDC

What am I doing wrong, here?


You are using the datalogger IDC count. Its not accurate; it shows a higher IDC than you really have. Its physically impossible to have above 100%IDC.
 

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Devoted Darkling
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Trevor said:
Approximate ranges are as follows:

450's with stock FPR: 400 - 499HP
450's with adjustable FPR: 381 - 510HP
I'm glad you put this in to words, Trevor. I was working this out for myself. I had a few self proclaimed "experts" telling me that 450cc injectors were wrong for my setup, and that I needed 550cc injectors.

I dynoed at 359 AWHP on pump gas with the engine knocking a little and killing the top of the pull. Calculate that out with a static DT loss of 85 HP (while not absolutely correct, I feel a static value based off of stock DT loss is more accurate than claiming 30 - 33% loss) and my car was making ~444 HP at the crank. Running in that tune pulled 109 MPH traps. Putting in race fuel and tuning it better put me to 114.75 MPH traps at the same boost level. My IDCs got down to the mid 80% range and timing peaked at 30*. In my opinion, the 450cc injectors are the perfect match for my setup. Matter of fact, there is still room for me to lean it out more, make more power, while still keeping the timing and knock in check. I'm yet to go below .92v on the logger @ 1.2 KG/CM². I should be able to get it to .90v without even thinking of knock running C12. If that doesn't get me to 116 MPH... well, so is life. ;)

I was considering upgrading to 660cc injectors soon in preperation for my next turbo upgrade (which is going to be a little less TD04 this time ;)), but I had already talked myself out of it based on the results I was seeing from the 450cc injectors and C12. If I put in anything larger than a 550cc injector the SAFC I have will not be able to lean the fuel down on C12, and even if it could get the car down to .92v, timing would go well over 30*, and that would not be good either.

550cc is the largest injector I would even consider for a DR500 / 13G car. Anything more than that is just a waste, and could lead to more harm than good.

I plan on dynoing my car again on C12 and seeing where she ends up this time. I'm will to bet I'll break the 400 AWHP mark. Add in the static DT loss, and I'll be really close to 500 HP at the crank. And since I have a stock FPR, that is right in line with your calcs.

Great post. I'm going to have fun helping to prove you right. :D
 

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J-Ville VR-4 said:
You are using the datalogger IDC count. Its not accurate; it shows a higher IDC than you really have. Its physically impossible to have above 100%IDC.
Right. So how do folks tune for 80.2% IDC? Can the values my logger reports be simply scaled by 100/122 = 82%? Perhaps Shiver can add that factor to the next release. ;)

Would timing remain within spec if I upgraded from 9B to 13G (250 to 324 practical max CFM = 29.6%) and from 360cc to 450cc (25% + some fuel pressure)? All I'd need is a SAFC-2?
 

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vehicular thaumaturgist
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bjmsam said:
Right. So how do folks tune for 80.2% IDC? Can the values my logger reports be simply scaled by 100/122 = 82%? Perhaps Shiver can add that factor to the next release. ;)

Would timing remain within spec if I upgraded from 9B to 13G (250 to 324 practical max CFM = 29.6%) and from 360cc to 450cc (25% + some fuel pressure)? All I'd need is a SAFC-2?
"Within spec"? Timing will be higher, but not unreasonable with that injector upgrade and the necessary correction. An S-AFC can easily take care of that.

-Chris
 

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bjmsam said:
450cc injectors would seem barely adequate for my 9Bs:
122% IDC * (360cc / 450cc) = 98% IDC
122% IDC * (360cc / 550cc) = 80% IDC

What am I doing wrong, here?
That math is wrong as you need to (^2) square it somewhere. Go to stealth316.com and look for his injector calculator web page.
 

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antero said:
That math is wrong as you need to (^2) square it somewhere. Go to stealth316.com and look for his injector calculator web page.
Uhh, no you don't. We aren't talking fuel pressures here.

-Chris
 

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ukyo said:
I'm glad you put this in to words, Trevor. I was working this out for myself. I had a few self proclaimed "experts" telling me that 450cc injectors were wrong for my setup, and that I needed 550cc injectors.
I still believe you need 550cc injectors if you really want to max out those turbos and make the most power possible. And no, I never proclaimed myself to be an expert, but I'll be sure to remember that little "slap" ...

Aside from the obvious need for additional fuel and TIMING, I simply do not like old, used injectors. Did you even have those 450cc injectors flow tested?

ukyo said:
If I want decent IDCs that will give me mid to high 20* timing, it would appear as though the limit on my car is 1.3 KG/CM² (18.5 PSI) leaned out to ~28% with C12 leaded race fuel. Leaned any more the car starts to knock, even with the leaded fuel in there.


For now I'm going to say the practical limit for my set up on C12 is 1.2 KG/CM2 leaned down to -30% correction. That is where I made the 114.75 MPH trap. I actually had a little more room to lean the fuel at that boost level, so it has the potential to net me higher traps. I don't think running higher boost is going to help me at this point until I do changes elsewhere in the system (as noted by pacman3000gt). But still... 114.75 MPH traps (with obvious room to improve with better tuning) running the stock ungutted MAS, DR500s, tiny 450cc injectors, MBC, DP and a lightweight flywheel... (basically I have ~$2,000 in the car for performance parts). IMO, that's a good return on the investment.
So, what? Now you're arguing with what you've witnessed and stated yourself?
 

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AdamVR4 said:
I still believe you need 550cc injectors if you really want to max out those turbos and make the most power possible. And no, I never proclaimed myself to be an expert, but I'll be sure to remember that little "slap" ...
Ummm... Did I say I was talking about you??? You can assume what you like, but I assure you 1 - You don't live around here, where I get the bulk of my "expert" advise and 2 - That "slap" was not intended for you.

AdamVR4 said:
Aside from the obvious need for additional fuel and TIMING, I simply do not like old, used injectors. Did you even have those 450cc injectors flow tested?
I'm making 30* of timing at redline and I still have room to pull fuel (on race fuel). Pulling fuel, as you know, means I will hit a little more timing as well. So I still don't see how my timing is suffering??? I make mid 20* on pump gas at 1.2 KG/CM², and 30* on race fuel at the same boost level. Maybe the timing is a little low for pump gas, but it seems to be doing just fine on race fuel.

And no, I did not have the injectors flow tested, cleaned, or otherwise looked at. I've had no blatant issues with fuel devliery. I'm still running the stock 88K mile fuel filter with the stock fuel rail loop, too.

AdamVR4 said:
So, what? Now you're arguing with what you've witnessed and stated yourself?
I'm not arguing anything. I found the perfect injector for my setup. I can basically control every aspect of the tune from a piggyback with no worries of a delicate balance. If I want more timing / power, all I'm just a few gallons of race fuel and a few negative correction clicks away from having it. And all of that with no worry of going too lean, running too much timing, or running out of correction room on the piggyback.

I feel that with 550cc injectors I would have to walk a thin line between leaning it out and getting too much timing. Thus far my experience with 450cc injectors has shown me that I can lean it until I see minute knock, and still have the timing right at 30*. I haven't tried yet, but I'm sure that if I lean 550cc injectors down an additional -12% on the SAFC timing will be above 30*, and it'll still be hitting .94v (race fuel). Now you only have 5% more fuel to play with (SAFC), and your timing is starting to get too high. What do you do? Let it sit there and run on the rich side with slightly too high timing? Richen it up and kill power to get the timing back in check? Lean it some more and hope the timing doesn't go overboard? I don't have that problem with my 450cc injectors.

550cc injectors may make more sense for my setup in two scenerios:

1 - More timing at pump gas corrections.

2 - More boost needing more fuel. This is an option, but I'm running the 17 PSI that DR rated the turbos to already. I thought about running more boost, but when I turned the boost up at the track last time all I got was knock counts. O²s looked good, but it was knocking all the same. Either my turbos can't produce anything much more than 17 PSI in their range or (as pacman3000gt already noted) I need to revisit my IC setup.

I just don't see how, from those numbers, you can think I would benefit hugely from 550cc injectors???
 

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ukyo said:
Ummm... Did I say I was talking about you??? You can assume what you like, but I assure you 1 - You don't live around here, where I get the bulk of my "expert" advise and 2 - That "slap" was not intended for you.



I'm making 30* of timing at redline and I still have room to pull fuel (on race fuel). Pulling fuel, as you know, means I will hit a little more timing as well. So I still don't see how my timing is suffering??? I make mid 20* on pump gas at 1.2 KG/CM², and 30* on race fuel at the same boost level. Maybe the timing is a little low for pump gas, but it seems to be doing just fine on race fuel.

And no, I did not have the injectors flow tested, cleaned, or otherwise looked at. I've had no blatant issues with fuel devliery. I'm still running the stock 88K mile fuel filter with the stock fuel rail loop, too.



I'm not arguing anything. I found the perfect injector for my setup. I can basically control every aspect of the tune from a piggyback with no worries of a delicate balance. If I want more timing / power, all I'm just a few gallons of race fuel and a few negative correction clicks away from having it. And all of that with no worry of going too lean, running too much timing, or running out of correction room on the piggyback.

I feel that with 550cc injectors I would have to walk a thin line between leaning it out and getting too much timing. Thus far my experience with 450cc injectors has shown me that I can lean it until I see minute knock, and still have the timing right at 30*. I haven't tried yet, but I'm sure that if I lean 550cc injectors down an additional -12% on the SAFC timing will be above 30*, and it'll still be hitting .94v (race fuel). Now you only have 5% more fuel to play with (SAFC), and your timing is starting to get too high. What do you do? Let it sit there and run on the rich side with slightly too high timing? Richen it up and kill power to get the timing back in check? Lean it some more and hope the timing doesn't go overboard? I don't have that problem with my 450cc injectors.

550cc injectors may make more sense for my setup in two scenerios:

1 - More timing at pump gas corrections.

2 - More boost needing more fuel. This is an option, but I'm running the 17 PSI that DR rated the turbos to already. I thought about running more boost, but when I turned the boost up at the track last time all I got was knock counts. O²s looked good, but it was knocking all the same. Either my turbos can't produce anything much more than 17 PSI in their range or (as pacman3000gt already noted) I need to revisit my IC setup.

I just don't see how, from those numbers, you can think I would benefit hugely from 550cc injectors???
Unless DR500's are incredibly inferior to 13G's, you're not maxing them out at 1.2 bar.

Something is wrong if you get knock beyond 1.2 bar. And it's not your IC set-up. No offense, but that's Paul's favorite recommendation to make... It's just simply not the case if you have proper fuel. 17+ psi isn't a lot of boost...

If your IC set-up is really holding you back, why have so many before you been able to make more power and run more boost through them without knock issues?

Perfect example is FastOldGuy... 13G's, stock SMIC's, 20 psi... We "hot-lapped" ;) the car on the dyno and it held 20 psi to redline with minimal knock counts (I saw 8 counts for a second above 6000 RPM) which could have undoubtedly been ironed out. It made 410 AWHP. He has oversized valves... That 20 psi number would have been higher had he had stock valves.

What kind of race gas were you running?

You mention you'll be over 30* with more fuel to play with if you run the 550's ... This sounds perfect to me. Lean it out as much as you can with the 550's and your timing may very well be at 34* at redline (arbitrary #) ... Turn the boost up HIGHER to compensate for the additional fuel and run better gas! Pure C16.

You basically wanted to know how you could make the most power... I think you can make MORE power with 550's than you can with 450's with your turbos.

If you were only running one DR500, I'd agree, 450's would be perfect :)

Or an AFPR would allow you to get the additional fuel and timing you could use beyond 1.2 bar, but something isn't right if you're seeing knock at those boost levels on race gas. Perhaps your injectors aren't flowing the same amount. I had 5000 mile old PTE 780cc injectors flowed and cleaned and one of them failed every test and flowed like shit. 5000 miles old. Just figured I'd throw that out there...
 

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Nice write up....Im looking to see what size injectors I would need for GT368's without overkill. Anyone have any ideas?
 
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