Tuning...just what does that mean??

[87LtdT]

Been a T owner for 8+ years now and have seen tuning tuning tuning mentioned about 3 zillion times...I assume there are some deep dark secrets laying therein, and I don't know what they are. I've never asked before because I get tired of looking like the only one who don't know

But as I age I'm getting used to being the only dumbass in the group, so forgive me for asking but just what does this "tuning" entail??

I see only fuel pressure, boost, tire and air bag pressure as the things that I can control at the track. I know there are multiple setting chips available, but I also see lots of guys in the 11's (my goal) with what appear to be fairly standard chips. I run a Lubrant 110+ w/28 degrees timing, and a little fuel pulled out at the launch.

So I go to the track, set the air bags at 25 psi pass side and 5 on the drivers side, and drop air pressure in ET Streets to about 13.5 psi which seems to be my optimal settings. Set boost to 25 and fp to 45 and I get pretty consistent 780mv O2 numbers, and about 1600-1625 peak EGT.

I run with C16 and have Direct Scan. Get no knock, and very seldom have any spark retard.

So how should I tune this bad boy if I don't like the times I get??

Thanks, Bob

 

[bruce]

TUNING,
my favorite subject.
And one I take lots of heat over.
There are two ways to tune, one is close enough to run, and the other is having the tune completely CORRECT.

Can you run an 11 with 009s?.
Yep.
But, at what expense?, pushing an engine with an injector that is static, IMO is dumb or stupid. You have no control of the curve that way. You hammer the injector on (well hopefully), and then just run enough pressure so that the LEAN spots don't bite you.
Note the, (well hopefully), if you try to blend an injector from any given duty cycle to full on there is a moment when the injector gets confused and it WILL CHATTER on and off a few times as it trues to go static. Oooops, that chattering is LEAN, and while at WOT having an engine go lean, is how you get a gasket collection of blown headgaskets.


OK, that leaves, trying to get things CORRECT.
It's easy then most people think, but it does involve some leg work. First off, there is solid data that you can use. ie, don't exceed a 85-90% DC. Then for figuring injector sizes just use what GM did. If you want to double the HP then just double the injector size. And about doubling the HP is just some exhuast work and making an adjustable WG. So you're instantly looking at 55 PPH injectors (30x2=60).
For like $200 you can get into even doing your own chips.
Granted it's not for everyone, but it ain't rocket science, by any means.
If you don't want to burn chips, then using a Translator Plus gets you timing, and WOT fuel corrections if you get the extender chip.

You'll never in a million years, image how good a car drives with a CORRECT calibration. While GM had to worry about the wierdest extremes of drivers, when you dial one in for yourself it's sweet.

 

[87LtdT]

Thanks for the response Bruce. I see that my MSD 50's are at 100% DC near the end of the run maxing out at about 105%.

I also see from Lubrant's chart that I only need a 40-42 lb/hr injector to run at 80% DC and go 110-112MPH...which about where I run.

So what is driving my 50 lb/hr injectors to go over 100%??

Bobs

 

[bruce]

Originally posted by 87LtdT
Thanks for the response Bruce. I see that my MSD 50's are at 100% DC near the end of the run maxing out at about 105%.

I also see from Lubrant's chart that I only need a 40-42 lb/hr injector to run at 80% DC and go 110-112MPH...which about where I run.

So what is driving my 50 lb/hr injectors to go over 100%??

If you're at 105 the games over, unless you want to start dialing in more FP.

I don't agree with Joe's math.
In my lil corner of the world, .55 BSFC is alot more reasonable of figure, and again in my lil world, I have to use the Fuel Air Power Enrichment table to add about 3% more fuel for every 3 secs in PE. So on a 12 sec pass that's another 12% more fuel so now that .55 is more like .65, and that's a fair distance off of .5.
While you might want to run those numbers (BSFC of .5) and use a FAST ecm, they don't hold water, again in my book, for a stock ecm.

All you have to do is look at your numbers, 110MPH at 105% DC and your done. Going 10% larger now in injector size only gets you to breaking even. You need to cool the intake charge, ie bigger turbo, FM, WI, propane, and or, go some serious injectors.

 

[87LtdT]

I dunno Bruce...something else seems wrong. Why do I need to to do any of those things when I seem to be equipped to run 11's?? Hel,l there are bunch of guys deep in the 11's with less hardware.

I see that my % DC rises with engine speed...might even be proportional. Would slowing the engine revs reduce duty cycle??

What is WI (water injection?) ?

Bob

 

[TurboDave]

Something is wrong, most likely in the chip commanding too much duty cycle.

You're running 50's at somewhere close to or just over 100% and still only running high 111mph's ???????

I also run MSD 50's, run 27# of boost, 29 degrees of WOT timing, and the highest duty cycle I've seen so far is 89% at the top of the run, and I have very little trouble running in the 117mph range.

My guess, without seeing what's in your chip, is there's probably too much fuel being commanded in one or more of your PE tables. That's generally the culprit.

I guess I have the added luxury of running the Translator + and Extender chip. This pretty much allows me unfettered tuning of the timing, and WOT fuel delivery without having to worry about the MAF maxxing out, so any adjustments I make to WOT fuel delivery actually happen.

 

[UNGN]

What size tires are you running and what RPM are you crossing the line at.

You can dwell on injector duty cycles until you are blue in the face, but if the car is crossing the line at 5400 RPM at 111 mph, 115 mph aint gonna happen.

"Tuning" involves much more that actual tuning. It's making sure the intercooler is cold before you run or making sure the brakes will hold the most boost that they can, to making sure all the intercooler hoses line up with no mismatch. 100's of little things that add up.

 

[87LtdT]

26 X 10" ET Streets....and at 5350 crossing the line with stock head and cam...converter that appears to be slipping at about 20%. So the car is bound up with either too small tire, an excessively slipping converter, or both. Will reducing the engine rpm by fixing either also reduce the injector duty cycle?? I ask because the duty cycle increases as engine speed increases...not sure why that occurs??

I appreciate your definition of tuning and agree 100%...makes much more sense than only adjusting fp and boost...because, correct me if I'm wrong please, when at the track and you are at the max boost you are willing to run and get to 760-780 O2 and/or 1600EGT there is little else to do. Or am I missing something??

Thanks, Bob

 

[azgn]

did you ever consider 1600 egt might be rich? ignore the 02 and watch for knock...turn fp down or boost up and see what happens to your egt...I agree something is up with your chip and it may just be way rich......if (by some miracle) your egt happens to go down when you lower pressure or up boost, you have found your culprit.......what you see ain't always what you get

BTW, that much slip in the converter is no good.........it could just be transmission slip and that will affect everything...

 

[Dean]

Originally posted by 87LtdT
Been a T owner for 8+ years now and have seen tuning tuning tuning mentioned about 3 zillion times...

Engine wise, I have always interpreted it as being optimizing what you have, taking it to the edge, and then backing it off a bit for a little safety margin. But it doesn't stop with the engine, continue with the transmission, chassis, suspension, etc. Something does strike me as amiss with your car... I run a very similar setup to you, but with significantly less WOT timing & boost (21*/~23 psi) I'm just over 113mph.

I have no experience with EGTs (yet), but looking at your O2 #s, I would consider it rich, IMO. I don't use C16... I use UNOCAL 100 Unleaded and take the O2s down to the .740 range. I'll probably get some flack for relying on NBO2 readings, but that is all I have used to date, so that is the reference I use. I have seen others refer to EGTs ~50* higher than you report. "Leaner is meaner, as long as you don't pop!"

Originally posted by 87LtdT
So what is driving my 50 lb/hr injectors to go over 100%??

100%+, but at what ms, and what RPM? Also, is the 100%+ only at the top end, or also at the top of 1st & 2nd (what ms & RPM?)? UNGN may be onto the source of your woes when he asked the question, "What size tires are you running and what RPM are you crossing the line at." Duty Cycle is a comparison of the actual injector on time compared to the total availabe time for the injector to run, so the higher the RPM, the less time there is. FYI, a sampling from one of my DS files:
Top of 1st - 5125 rpm, 22.71 InjPW, 97.0% InjDC, 831 O2s
Top of 2nd - 5125 rpm, 22.02 InjPW, 94.0% InjDC, 804 O2s
Top of 3rd - 5100 rpm, 20.75 InjPW, 88.2% InjDC, 765 O2s
Top End (locked) - 5300 rpm, 19.93 InjPW, 88.0% InjDC, 737 O2s

InjPW is a longer calculation that I don't fully understans.


A few "tuning" things to consider:

- Plugs: How do they look? Is it an appropriate heat range? I have had good results with Autolite 23s gapped @ 0.032.

- Ignition components: In good working order? How do you know?

- Rear Tires: Taller than ~stock height tires will reduce trap RPMs. You mentioned you had ET Streets. 26x10.5-15s (~26" tall)? The 113 was on Nitto DRs, ~26"tall (~1.80 60'). If you had 27" tires you would go through the top end ~200-300 rpms lower. They won't help so much at the top of gears, though... perhaps some.

- Look at your shift point RPMs and see if you are within a reasonable range. Spinning a stock cam/head/intake 3.8 above ~5300-5400 gets you out of your power band with smaller turbos like our's. I'm shifting @ ~5100, and each shift drops the RPMs ~500, and the convertor l/u drops ~600. My peak HP of ~410 is at ~4500, ~400 @ 4600. At 5100 I'm still making ~375, and ~370 @ 5200, but ~355 @ 5300, ~345 @ 5400, ~330 @ 5500.

HTH

 

[Dean]

I was typing, got distracted, came back, and there were more posts...


Is your converter a l/u?

:-Dean

 

[bruce]

Originally posted by 87LtdT
I dunno Bruce...something else seems wrong. Why do I need to to do any of those things when I seem to be equipped to run 11's?? Hel,l there are bunch of guys deep in the 11's with less hardware.

I see that my % DC rises with engine speed...might even be proportional. Would slowing the engine revs reduce duty cycle??

What is WI (water injection?) ?

Bob

Do you want to go fast reliably?.
Do you like running on the ragged edge?
Do you perfer to use logic, or just follow the crowd?.

There are lots of answers, and everyone is entitled to their opinion.

Duty cycle is a function of injector ON time compared to available time for it to be one. At 6,000 RPM you have 20 msec for 2 crank revolutions, so a 20 msec pulse width would be 100% DC. At 3,000 rpm you have 40 msec for the same 2 crank revolutions, so that same 20 msec PW is now a 50% DC.

This should make it more clear about how critical injector size gets, especially at the HIGHER RPM levels.
ANY injector will work at the lower RPM levels.
Look at how 50% changes to 100% so easily!.
While you can get by in a way with smaller injectors, the instant you get serious at the higher rom and boost levels the whole strategy of small injectors just doesn't make good sense.

 

[87LtdT]

Converter is a self locking Yank...but it is slipping at approx 20%...so it isn't locking very well...I'm working on that. Trans very recently freshened by Lonnie Diers and shifts awesome..so I think I'm OK there.

My DS files show 5200 at 2-3 shift with 21.74ms injection time = 94% usage...at 5100 rpm (to compare to your info) it's 22.35msec at 95% but then goes on up because of slippage to 5400 which is in the 105% range. Dropping trap rpm to 5100 gets me to 92.5%...seems my commanded pulse width is a bit too much.

DS shows commanded PW is 21.1msec after 2-3 shift and climbs to 23.6 by the traps.

I use Autolite 23's at .034"...have a fairly new coil pack and all seems OK.

Appreciate all of your interest.

Bob

 

[azgn]

please define a "self locking Yank"...you are slipping badly

I go thru the traps at 124+ at 5100 with my converter locked....even with it unlocked I am at 5600 or so....5 disc Precision 3600 stall

do not get hung up on Bruce's psyco-babble...it will not help you go faster...concentrate on the basics and the basics as I see them are you are slipping badly somewhere (and throughout the gears....)

 

[Two Lane]

I appreciate bruce giving the data behind his advice.

Sure beats: "Do "this", then "that" (cuz I sez so).
---------------------------------------------------------------------------

bruce, you've done a great job pointing out the potential hazards
from running injectors that are too small.

Any functional downside to running larger injectors, e.g., 72 or 83s, for moderate street/strip duty?

TIA

 

[87LtdT]

Woody, don't think I'm rich, but don't have recent data to prove it. I've only made 5 runs in the past year with the 28 degree chip and recorded only 3 of them...with nearly identical settings. But in previous years with the 26 degree chip it is clear that EGT are behaving correctly....eg

24 boost 40 fp 1636 EGT
24 boost 36 fp 1681 EGT
24 boost 45 fp 1585 EGT
22 boost 45 fp 1547 EGT

The reason for so few runs is converter probs...long story but all last year was trying to get an ATI to work...unsucessfully. Over the winter went with a Yank which features a self locking gizmo tht reacts at high torque levels to lock itself. I've calculated that at 100MPH my engine speed is 4322 rpm...might not be exactly correct but I've consisitently used that number to calculate slippage...unlocked D5 was 13%, 8" non-locking ATI was 24%, 9" non-locking ATI was 21% and the self locking Yank was 20%. Just ran the Yank early Aug and have just last week tried to contact them for a standard (no gizmos) locker.

What I think I've learned here is:
1) Engine speed too high (knew that but it's certainly been reinforced)...even if I get to 5% slip a 115MPH trap speed would be approx 5200 rpm...so I think I need 28" tall tires too. UNGN said that best

2) Bruce did a good job of explaining injector duty cycle, and while his convictions are clear, I don't know that I agree that I need mongo size injectors to go mid-high 11's.

3) It appears my chip is commanding a bit too much fuel. Dean's data was helpful to compare to. How is fueling done in the chip?? Is the injector pulse width specified at engine rpm or is the percent usage spec'd??. Watching the DS files I can see that the injector pulse width steadily increases as I go thru 3rd gear...from 21.74 msec to 23.6. Does that sound a bit too rich?? Who are our best chip burners??

4) I've long suspected that my intake to head and even stronger suspected my head to exhaust alignment is not pretty...been too lazy to check. Looks like I'm gonna have to get off my butt and do so...I'll check exhaust alignment first.

5) The interest level of other turbo guys is fantastic...where else can you get help from across the nation from guys you've never met?? I know for sure that other similar web sites on brand X cars do not react as quickly, knowledgeably, or in such an interested helpful manner...I only wish I was knowledgeable enough to repay others with similar well thought advice.

Thanks, Bob

 

[John Larkin]

Bob, your combo is somewhat similar to mine (i.e. unopened long block). I was @ 38 lbs FP, 25 psi running the times below with 1550-1600 EGT. That was the fastest MPH I ran that day, but also my converter was not locked and the 60' was 1.77. Fixing both those problems and maybe increasing FP and boost will help. I only saw 0.7KR on C16 so I think it's safe for now but faster will take some planning.

Therefore, I think I have enough fuel delivery capacity to raise boost, but I have 10% more injector than you and 28" tires as well. It's my belief as well that you need more injector and bigger tires too. I need DirectScan bad.

 

[turbov6joe]

I would be reluctant to say that 1600º EGT is "rich" with OE headers...by any standards. I think for your application, 1600º is right about on the safe/pushing the envelope line. I like to tune for 1580º-1600º myself. This ensures there is enough fuel for the safety net minded individual. I would NOT give much credit to the O2 voltage readings your seeing. The OE style O2 sensor is NOT wide-band, and is NOT able to give you accurate readings entirely. It is at best, a good reference for you to compare with EGT readings throughout a pass. There is no denying that a .6xx or low .7xx something O2 is leaner in most cases. On my 10 second GN, the EGT would be around 1580º+, and the O2's would be in the high .6xx range (tell ya something???.) If your EGT probe has been placed properly, then I would bank on those numbers more heavily. Tuning like anything else takes patience and a bit of common sense. There are SO many racers out there that shoot for unreal EGT #'s and run really fast to boot....but one must ask themselves, how often do I want to replace headgaskets or tear apart the motor for re-builds??? Along with this is the age old question of how much octaine should I use? IMO the higher the octane (to a point), the higher that margin of safety is in case something goes wrong IE...the WG bleeder hose pops off, you forget to put the regulator hose back on after adjusting the FP, or something that Mr.Murphey decides to do while he's riding shotgun on your next pass! My idea of tuning consists of checking and/or replacing all sensors every season, finding the perfect gap on the plugs, port matching all parts, cleaning the injectors, changing the fuel filter every season irregardless of miles etc... If you keep your EGT's and O2's in the "range", use enough octaine for your performance level, and keep the motor and suspension in tip-top condition, then your tuned as far as I'm concerned. Internal motor problems or the things you cannot see or control are just that, things you cannot see or control. Yes you cannot see your piston rings or valves, but a cpmpression check and a leakdown test every year cannot hurt>>>>just takes time. I also use a boost gauge with vacume to use as a reference. If you know what your "normal" vacume is at idle, then see it slowly decrease over time, that should tell you that something is wrong and needs attention. Anyhow, I'm done with this short book (especially before what I say is coined psyco-babble.) Hope any of it helps!

 

[Dean]

Originally posted by 87LtdT
...How is fueling done in the chip?? Is the injector pulse width specified at engine rpm or is the percent usage spec'd?

Here's an excerpt what I got from the same question on another thread ( Falling O2s ):


Posted by TurboBob:

... All fuel delivered is as a result of the MAF reading.

The ECM takes MAF, divides out RPM so it knows how much air is getting into one cylinder on one cycle. takes this air per cylinder and multiplies it by AF ratio (visible on DS) then converts it to pulsewidth based on injector size. (I left the integrator and BLM out for simplicity)...

 

[bruce]

Originally posted by azgn

do not get hung up on Bruce's psyco-babble...it will not help you go faster...concentrate on the basics and the basics as I see them are you are slipping badly somewhere (and throughout the gears....)

Ya, don't let actually trying to understand what's going on get in the way of 15 year old data.

Just throw parts at it, and upgrade the injectors 5x, and think you're saving money.