T-Smec 2.5 G-head Thoughts

[1BADVAN]

I have been tuning off and on for long time, and often thought that my van just doesn't have the top end power I know it should have. On another thread (http://www.turbo-mopar.com/forums/showthread.php?65487-14.73-on-15-psi-in-my-Voyager-Seems-like-it-should-be-faster-Suggestions-welcome&highlight=) I posted my thoughts on that, and Juggy commented about needing more timing.

So over the last 2 days i studied lots of different templates, looking at the timing curve and the calculated total timing.

This is the 'Advance from RPM2' or '00GOVNER'

41319

In this pic the Light Blue= T-smec G-head cal, Green= swirl head (both 2.5) I noticed that as the RPM goes up the swirl cal adds timing and the G-head does not.


So i assume that the "swirl" curve is closer to the factory engineered curve of timing needed dependnet on RPM. So instead of using the G-head curve I took the Swirl curve and added 10* of timing to every point so it is the same Shape but more timing. Like this

41325
Dark blue=Swirl head cal, Green=G-head template, Light Blue= What I did.-

Result= WAY MORE POWER! the van is now on 4 psi less (12 instead of 16) and according the the Butt Dyno the current low boost cal would smoke the old one.

That only makes sense to me, that as the engine spins faster it needs more timing Just like the swirl cal. I am not done tuning it yet but now it runs so much better and smoother across the RPM range, but Especially has significantly more power over 4000 RPM.

IDK but i would suggest that maybe Rob can update the G-head template in T-SMEC. From what i remember that was based off a cal that someone else did. I like some of the drive-ability issues it helps with but its is lacking its potential.

What are your thoughts everybody?

[1BADVAN]

In addition I believe the Pump Eff table is also off a bit. I started noticing what i would call "Breaking Up" over 5000 RPM in 2nd gear (not in first as it revs so fast). So as i started hunting the problem i noticed that the A/Fs would be a steady 11.5 until 5000 RPM, then it would Drop to 10.8. So the added fuel was killing power.

So some hunting found that the Pump eff table on the G-Head cal was higher than the others. I adjusted mine to be in-between the 2 but closer to the lower one and it fixed it! Again I think that the template would better serve a wide group if it was closer to the stock curve than this one is.
I have only one test so far so more adjusting to come.

41320
Again blue=unmodified G-head cal. Green= unmodified swirl cal. (seems to be the same on whichever i choose)

[turbovanman²]

Well PE tables are different for every engine so that is a given that what will work on yours won't work on Joe's etc.

As for the timing table, I thought that one was or is for cruise, IE like a vacuum advance on a dizzy setup.

[1BADVAN]

Well PE tables are different for every engine so that is a given that what will work on yours won't work on Joe's etc.
Right, what i am saying is that the Template is based off of a custom one. it should be the standard Chrysler one like all the others.



As for the timing table, I thought that one was or is for cruise, IE like a vacuum advance on a dizzy setup.

No from what i understand that is the base timing, or the timing the computer first looks at and then it adds the timing number (positive or negative) from the MAP tables to get the "Total" timing.

They talk about about it here starting in post #677 http://www.turbo-mopar.com/forums/showthread.php?45009-MPTuner&p=862311&highlight=wotmap#post862311

[turbovanman²]

Right, what i am saying is that the Template is based off of "Joes" it should be the standard Chrysler one like all the others. If my engine with decent mods didn't run good on it a stock one wouldn't like it at all.

Sorry, not sure what your saying here? Rob's stage cals are slightly tweaked and rely on us to modify the PE table to suit our needs.



No from what i understand that is the base timing, or the timing the computer first looks at and then it adds the timing number (positive or negative) from the MAP tables to get the "Total" timing.

They talk about about it here starting in post #677 http://www.turbo-mopar.com/forums/showthread.php?45009-MPTuner&p=862311&highlight=wotmap#post862311

Ok, so what map is that, hard to see what it is, but to me, looks like the "Advancefromrpm2" table? Which is the mechanical advance like a dizzy, not vacuum advance like I thought.

[1BADVAN]

Sorry, not sure what your saying here? Rob's stage cals are slightly tweaked and rely on us to modify the PE table to suit our needs.



Ok, so what map is that, hard to see what it is, but to me, looks like the "Advancefromrpm2" table? Which is the mechanical advance like a dizzy, not vacuum advance like I thought.

I think i fixed my post to make it a bit clearer. And as for the mechanical vs vacuum basically you are right they work like that. What i am saying is i think the curve on the 'AdvancefromRPM2' table is not optimum.
Not the right curve, it adds timing at low RPMs but not at Higher RPMs so i changed it so it added timing everywhere, and the results were Great! I will post up my curve in a second if i can pull it up.

[turbovanman²]

I think i fixed my post to make it a bit clearer. And as for the mechanical vs vacuum basically you are right they work like that. What i am saying is i think the curve on the 'AdvancefromRPM2' table is not optimum.
Not the right curve, it adds timing at low RPMs but not at Higher RPMs so i changed it so it added timing everywhere, and the results were Great! I will post up my curve in a second if i can pull it up.

Ok, so we are on the same page, :nod:

Yeah, I crank mine too, its not as much as the G-head cal Rob has posted in the Stage IV cals.

[1BADVAN]

added a pic and tried to clarify the first post. Thats what i get for trying to type fast inbetween things at work.

[Force Fed Mopar]

You could have added timing to the map timing tables instead and done the same thing.

[zin]

Makes sense... The G-head is not as "fast" a chamber, so it would need more "lead"/timing to get peak pressure in the sweet spot... I think that's the biggest problem with the cal I have right now, not enough timing and too much fuel.

Maybe one of these days life will cut me a break and let me spend some money on "toys" so I can get a burner and fix it!

Mike

[1BADVAN]

You could have added timing to the map timing tables instead and done the same thing.

Not true, the map timing tables adds timing to all of the RPM range, what i did adds timing to the parts that need it. or were not given it originally. This is why previously the power would fall off after 4500 now it continues to pull until 5500, like the GLHS i drive


Makes sense... The G-head is not as "fast" a chamber, so it would need more "lead"/timing to get peak pressure in the sweet spot... I think that's the biggest problem with the cal I have right now, not enough timing and too much fuel.

Maybe one of these days life will cut me a break and let me spend some money on "toys" so I can get a burner and fix it!
Mike

edit: I misunderstood what you mean by "lead" initially, if you read this before this edit. Yes it needs more advance or "lead"

I have done some brief google searching, and found that some SRT4 guys have found this same problems that some cheap vendors would just put a straight line timing advance instead of ramping it up with the RPM and they have noticed that is not optimal.

In our case this seems to just be a rarely explored with area of the G-headed 2.5. I am just trying to make it better and maybe correlate with you guys to see if my theories so far have a problem.

[zin]

I haven't messed with tuning much for the above reasons, but I've trolled around and like to learn. Anyway, I always thought it would be best to tune/optimize the engine off of boost first, pretty much tune it for n/a, then modify that tune to compensate for boost... Perhaps lifting the timing curves from the carb'd MP calibrations as a starting point?

I imagine that it could be a little dangerous if one went to high boost too quickly, but if one were to take their time and start small, it would seem like you'd get a more optimum result...

For instance, in my experience with other engines, it is surprisingly common for an engine with flat top pistons and 2 valves/cylinder to run their best with 34-38* of total timing all other considerations ignored (yes, there's always an exception, but Cosworths don't follow "the rules").

It seems like that is where you'd want to start, then back it off 1-2* per PSI of boost, at least as a starting point... But, maybe I'm just coming at this from a different angle?

Mike

[1BADVAN]

I haven't messed with tuning much for the above reasons, but I've trolled around and like to learn. Anyway, I always thought it would be best to tune/optimize the engine off of boost first, pretty much tune it for n/a, then modify that tune to compensate for boost... Perhaps lifting the timing curves from the carb'd MP calibrations as a starting point?

I imagine that it could be a little dangerous if one went to high boost too quickly, but if one were to take their time and start small, it would seem like you'd get a more optimum result...

For instance, in my experience with other engines, it is surprisingly common for an engine with flat top pistons and 2 valves/cylinder to run their best with 34-38* of total timing all other considerations ignored (yes, there's always an exception, but Cosworths don't follow "the rules").

It seems like that is where you'd want to start, then back it off 1-2* per PSI of boost, at least as a starting point... But, maybe I'm just coming at this from a different angle?

Mike

That's what i am thinking. In reality we can't do a no boost but we can do a low boost. I kind of go mid-range my lowest boost is 7 psi but I have tuned at 11psi as i figure it is a safe-ish level to test with.

[zin]

Still makes boost if the waste-gate arm is disconnected?... I can see that at the higher RPMs, lots of volume there, but at lower RPM, I would think it would struggle to make boost, maybe act like it has a restricted exhaust (because it does!)...

At any rate, good to hear I'm not ignorant of some turbo tuning axiom!

Mike

[1BADVAN]

You could have added timing to the map timing tables instead and done the same thing.
To edit/ add to what i previously said that yes you are correct i could have added x amount of timing across the MAP tables to get a similar result, IF the RPM curve was good to begin with.

[1BADVAN]

Just added a bit more timing so the RPM curve is now 14* advanced over a swirl head. On 11 psi you hear the tires at the edge of slipping (just a bit of squeal). These are not small stock tires either.
Needless to say i am loving this new power band!

[Force Fed Mopar]

Cool, really when you compare total timing there isn't that much difference between the two from the factory, except the timing comes in faster and is different in high vacuum. That said, the general concensus seems to be that bathtub heads like lots of timing. The timing curve for them is very much like the old V8's.

[1BADVAN]

Cool, really when you compare total timing there isn't that much difference between the two from the factory, except the timing comes in faster and is different in high vacuum. That said, the general concensus seems to be that bathtub heads like lots of timing. The timing curve for them is very much like the old V8's.

What do you mean? Just trying to clarify. Are you comparing the factory g head cal to the factory swirl cals for the 2.2?

[Force Fed Mopar]

Yeah, but I could be wrong lol, I'm going off memory and not near my computer. I may be thinking of 2.2 versus 2.5 instead.

[1BADVAN]

Just to add, i think my favorite part about this new timing is the amazing increase in throttle response. From a roll stabbing the throttle responds so much faster it feels like a non turbo car. I love it!
I am planning on going to the track on Friday so i am going to try upping the boost tomorrow to 16 psi with this timing and see how it responds.

[turbovanman²]

Cool, really when you compare total timing there isn't that much difference between the two from the factory, except the timing comes in faster and is different in high vacuum. That said, the general concensus seems to be that bathtub heads like lots of timing. The timing curve for them is very much like the old V8's.

Correct, swirl piston engines that use G-heads have a lower compression and need a ton of timing due to the dead chamber.

[Force Fed Mopar]

Looking at the cals in MP Tune, basically the higher the boost goes, the more the total timing becomes the same. Conversely, the at the lower boost levels and in vacuum, the bathtub uses much more timing. At 10 psi, Rob's custom 2.5 G-head ATX cal has 8-10* more than the swirl cal does.

[1BADVAN]

I am starting to think all i did was a waste of time. IDK what happened but today it just wants to detonate no matter what boost from 4-5k i even put in my old cal that used to run great and that did the same thing. Another weird thing i have had happen before when things go all weird is that the engine just started idling 200 lower than it usually does????
For the detonation, my guess is that the past few days have been about 20* cooler, but Why doesn't the old cal work, and why does it idle lower :mad:

[smdandb2]

I am starting to think all i did was a waste of time. IDK what happened but today it just wants to detonate no matter what boost from 4-5k i even put in my old cal that used to run great and that did the same thing. Another weird thing i have had happen before when things go all weird is that the engine just started idling 200 lower than it usually does????
For the detonation, my guess is that the past few days have been about 20* cooler, but Why doesn't the old cal work, and why does it idle lower :mad:

Those are the exact demons I have been fighting. My idle stays the same, but one day I will have it running great and knock free and the next day it just wants to light up the CEL everywhere.

I think I am going to start checking my plugs more frequently. If there is really as much knock as the sensor sees than the plugs should show it too I would imagine.

I suspect you have a different issue though. What kind of vacuum are you seeing? What are your air/fuels under boost now?

[1BADVAN]

Those are the exact demons I have been fighting. My idle stays the same, but one day I will have it running great and knock free and the next day it just wants to light up the CEL everywhere.

I think I am going to start checking my plugs more frequently. If there is really as much knock as the sensor sees than the plugs should show it too I would imagine.

I suspect you have a different issue though. What kind of vacuum are you seeing? What are your air/fuels under boost now?
It seems that the knock picks up more if it is hot. I let it sit for a few hours and it is cooler out, again it runs fine and the idle is back up to what it was???
I only have 8 inches of vacuum, and 11.5-11.7 A/Fs I know that is on the leaner side but i am working on that.

[smdandb2]

8" seems super low.

The Lancer pulls about .4-.5bar (11-14"ish).

[88C/S]

Have you checked the cam/ distributor timing. I had 11" at idle. Checked the cam and found it was retarded and advanced it to where it should be and now I have 20" at idle. I have a ported 287 G-head that was CC'd, with +1 valves stock 2-piece, TU cast header and 3" exhaust. The block is a stock '89 TII w/.020 mahles.

[turbovanman²]

8" is really low, even at your altitude, I would suspect maybe the timing belt jumped.

And you found the other issue with a G-head, your on the ragged edge so a temp change and it detonates like a mofo, :(

[Force Fed Mopar]

My 2.5 idles at 20" also. Another thing, sometimes knock sensors are overly sensitive, and the stock knock threshold is pretty conservative anyway. See my thread about it here http://www.turbo-mopar.com/forums/showthread.php?65145-Knock-voltage-readings-and-thresholds&highlight=

[1BADVAN]

My 2.5 idles at 20" also. Another thing, sometimes knock sensors are overly sensitive, and the stock knock threshold is pretty conservative anyway. See my thread about it here http://www.turbo-mopar.com/forums/showthread.php?65145-Knock-voltage-readings-and-thresholds&highlight=
I have roughly scanned that but i will have to look into it more. -Thanks

Thanks all of you on the cam. I will have to check the Cam, Maybe It jumped a tooth, but I probably just have the adjustable gear messed up. I thought i had it set at zero. It has had low vacuum for years i noticed it when i switched to a big FMIC and thought it was that.

Any tips on setting the cam? I know how to do it with a stock pully but how a bout for making sure the adjustable one is right?

I have heard things like adjust it until you get Max vacuum. Is that just a myth or are there tricks like that?

[smdandb2]

I've never seen a vehicle idle at 20in/hg up here, LOL. That would be neat!

On decel I see about 23in/hg. Looking at my math from last night I think I was off a bit. I usually see about 14in/hg at idle in the Lancer. I retarded the cam about 5 degrees before I broke it, so I am not sure what its actually idling at now. I never really looked.

[speedfreek500]

Is the adj cam gear a new one that fits on so the bolts are on the outside? i had an old one that was backwards and made a collar so i could flip the gear around so i could adjust it.

If you pull the cam gear off you will see the slot for the key way, if you look just above it there will be a small hole in line with it. I used that hole to line my cam up inbetween the 2 bolts at the front cam tower with the valve cover off. You could count up 2 ridges from the front of the valve cover if you didn't want to remove it.

http://i757.photobucket.com/albums/xx212/speedfreek500/adj.jpg

[turbovanman²]

I have roughly scanned that but i will have to look into it more. -Thanks

Thanks all of you on the cam. I will have to check the Cam, Maybe It jumped a tooth, but I probably just have the adjustable gear messed up. I thought i had it set at zero. It has had low vacuum for years i noticed it when i switched to a big FMIC and thought it was that.

Any tips on setting the cam? I know how to do it with a stock pully but how a bout for making sure the adjustable one is right?

I have heard things like adjust it until you get Max vacuum. Is that just a myth or are there tricks like that?

When I had my 8 valve, I played alot with cam timing, I found that adjusting it for max compression made it awesome around town and the midrange rocked but it stopped revving around 4500 rpm. So you can do that then back off to suit your driving habits but of course, the best thing is to actually degree it so you know where 0 is.

[1BADVAN]

so I retarded the cam all that the adjuster would let me and that netted a 7" of vacuum.
I advanced the cam all the way and that netted only 9-10" of Vacuum.

Both seem way low still. I find it hard to believe it is that far off to be more than one tooth off on the belt, it just runs too good in my opinion.

I ran a compression test and it reads 90 across the board. With the cam advanced it went up to 120ish.
I am guessing it is so low do to the low Compression ratio.
Any thoughts guys??

[turbovanman²]

150 is the normal I've seen, 120 is about normal for a higher mileage engine.

[1BADVAN]

150 is the normal I've seen, 120 is about normal for a higher mileage engine.
I guess i should add that my engine has less than 4,000 miles would those numbers change with the lower compression?

[turbovanman²]

I guess i should add that my engine has less than 4,000 miles would those numbers change with the lower compression?

Forgot you have a G-head, so 110-120 should be about right.

[smdandb2]

Silly question, what kind of boost gauge do you have? Have you tried another?

[1BADVAN]

I advanced the cam, and the engine couldn't flow air over 4200 the A/Fs went straight to 9.0 lol, Then i retarded the cam and it was way laggy and no low end, so I guessed by deduction the cam was on the right tooth.

so i then changed my throttle body and gasket, and i know have 14"! I think my Idle speed motor was bad, maybe causing a constant leak. The new throttle body is a 52mm, I guess i will see how that affects the tune, it is now all messed up from chasing all these demons, hopefully i can find an original cal somewhere. I want to get it running good for the track on Friday.

Makes me wonder if the low compression test numbers is due to the cheap Harbor freight gauge. I will have to try a different gauge sometime.

[Force Fed Mopar]

Just go back to the 2.5 G-head cal and start from there again.