Carb msd6 set up ideas!

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cnddodgehead

cnddodgehead

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Ok Looking for some guidance. here's what I have
2006 Grand Cherokee 6.1 . stock . (for now }
Msd 6
Indy mod man
750 cfm holly vacuum secondary

I started the engine last week WOW merry xmas. (2 years looking at it .) felt real good.

So after smoking myself out finding small leaks and things I finally got the msd and my laptop to talk to each other . timing curve at idle was pre-set 10 degrees .

I played with a bit and so far Ive left it at 12 degrees, some hot starting issues may go back to10degrees.


So my questions are . jets any thoughts of what might be best for now also timing and map ideas?
 
I have a different setup so our timing curves will be different. I have very low choppy intake vaccuum so I deactivated the map by neutralizing the map curve. I also run a mechanical distributor type curve. I run 5 deg advance at idol and run from 5 to 22 deg in a straight line from 1500 to 2500 rpm. May be a bit aggressive for you though.
 
My 5.7 with a comp cam 268 has initial timing at 6-8 I think, I also had some hot start issues when timing was 11-12* mine Ramps twice, about 20-22 deg at 3500rpm ish, then levels out and jumps to 24 by 4500ish. Pm me if you want with a email address I think I have a screen shot of the factory 6.1 WOT spark table I can email ya when I get home.

Joe
 
Your cylinder pressure with that intake will be pretty aweful

OK folks...One important point here.....he's running a carb intake....and one that has pitiful low end signal.

Your EFI curves are irrelevant to this discussion.

Sorry to be blunt..but its a fact.


I am running 21 at idle going as high as 25 all in at 3500

In fact...my mid range went thru the roof when I upped it from 16 deg startpoint to 21.

No pinging...plugs look fine, no baulking on the starter...and I run my MAP so it feeds in an xtra 11 deg below 8psi for cruising.


NOW - I very much doubt you could get away with this curve with EFI...or even a better intake...but I think you could run 16 initial without a care in the world with the Modman and factory cam

I have been and more....for 18 mths and my pistons are still intact.
 
This was the curve I ran for the first 6 mths.

Since then Ive upped the initial to 21, dropped the all in by 2 degrees and dropped the MAP by 2 degrees.....had it like this at the teack and on the street for twelve mths.

Yep...the Mdman really is apiece of junk.

 
Rat,

I figured you'd chime I when I saw his set-up, that's crazy the difference in timing EFI to carb/modman... Yours as dyno tuned too wasn't it?

Joe
 
Correct Joeboy - I had people on stand by listening for any pinging or knock....

I never would have tried that much timing...but a "guru" on the Speedtalk forum walked me thru the whole rationale....after listening to my tuning efforts and detailing my cam timing.....He was confident the motor would take significantly more timing than the 10 initial I wanted to start with...

My only advisory would be that the factory stick may not bleed off quite so much pressure - but there's probably not a lot in it.
 
Wow rat that's aggressive! When I left it at 10 ,It started hot with no issues . At 12 im having hot start issues. Where I have to feed it fuel . Right now im running open headers . may wait a bit before I really start to be more serious about your type of advance. Joy I will pm you !

You boys know of any other exhaust kits other than TTi ? Canadian dollars in the ditch because of low oil prices.
 
So let me understand this u are running 21 degrees intial timing and all in time by 3000 of 26 degrees

Just wondering as where I should start
I am running stock 2010 5.7 truck hemis dele rock dual carb kit and hemi 6 controller. Looking for mostly safe but max power at wot any suggestions appreciated
 
Unfortunately guys, I cant ell you what would be "safe" for particular combos.....all I can suggest is you use the usual signal points to determine how much is too much...

- Baulking on the starter
- Pinging under load...(be very vigilent when testing this..best to do it on a dyno with a "listener" standing by
- Checking plugs for "speckling" which indicates detonation


CNCDodge - you might well find your hot start "issues" are because you're not getting enough fuel from the pump shot to create a proper mixture...and the timing is a secondary issue - maybe try a bigger pump shot and then advance to timing and see what it does?


I will be swapping to a Edelbrock Dual Quad dual plane intake early this year....and Ill be backing the timing right off as a start point - probably 10 initial to 23 total and then start tuning and trialling...more in line with Hemi Joe's timing line.
 
Badasspullin said:
So let me understand this u are running 21 degrees intial timing and all in time by 3000 of 26 degrees

Just wondering as where I should start
I am running stock 2010 5.7 truck hemis dele rock dual carb kit and hemi 6 controller. Looking for mostly safe but max power at wot any suggestions appreciated
Click to expand...

Now 21 deg initial....23 total..not inc MAP timing which is added at cruise.

I would start at a more conservative point...like 10 or 15 initial to 23 total and see how it behaves......
 
Rat Patrol said:
This was the curve I ran for the first 6 mths.

Since then Ive upped the initial to 21, dropped the all in by 2 degrees and dropped the MAP by 2 degrees.....had it like this at the teack and on the street for twelve mths.

Yep...the Mdman really is apiece of junk.

Click to expand...

Here's an interesting question for you though. What about a ModMan running EFI? I can concur that when I had my ModMan and carb I could run some pretty high timing without any noticeable knock, though I can't necessarily say it had any more power. I was more just trying anything as I was fighting the transition between cruise and power (if you ever stabbed the throttle the thing was almost just die, but if you rolled into it, it would pull fairly well). I've since moved to EFI, but still have the same intake with a 4 bbl throttle body on top.

Is the extra advance more just an issue with poor fuel delivery at lower rpm/throttle openings? If that's the case it would seem EFI is probably less of a concern (port injection EFI especially as opposed to TBI), but I was just curious your thoughts. As an engineer I like getting into the "why" of things more than just the results.
 
ok Rat that is where im thinking . Starting at the lows . as for fuel . hmmm!
running a quick fuel pump and regulator . at idle around 5 psi . in the garage at approx. 3500 rpm 4.5 to 5 psi . any thoughts?
ran my rb 512 stoker at 5 psi ran awesome.
6.1 so far seems too like it. had buy better fuel now . brake in fuel was 89 oc.
I now have 93 oc . seems to run much smoother
 
Hey Ratpatrol just thinking . about the fuel thing . so far at the 10 degree all my starting hot or cold were no real issues . never had to give it fuel .
it set at 12 now starts cold easy , one shot with the choke on away we go . its the hot issue for sure .
I think until I get an exhaust system it will be really unproductive to mess to much with
it ,
As for fuel injection . is I wanted to go that root I would just slap the intake back on . I personally have no real interest right now but its always good to know about it.
 
Here's what Ive worked out..

The problem with the Modman stems more from the loss of signal between the cyl chamber and the carb than any issue with fuel distribution.

I used a heat gun on my exhaust and didnt detect a huge variation between temps on all header tubes.

So this lousy signal is caused by a combination of an excessive sized plenum ( the ratio of volume to carb is much greater than your normal single plane intake), an - the fairly poor runner angle and length.

So with a vac sec carb, the transition results in an inadequate flow of fuel - partly because of poor vaccuum draw and partly because of plenum size - and the resulting lean bog.

I managed to overcome the issue to 90% effectiveness by drilling the shooters, running two carbs and building a divider.

Advancing the timing to compensate for rubbish cylinder pressure also improved responsiveness.

However, at the track, the car still pulls a better 60 if I roll on the pedal quickly instead of stomping on it....once again proof of a lazy signal.

Using a 830 Holley DP - the twin pump shooters overcame the bog and resulted in similar 60ft times to my dual quad set up...but at the top end mph suffered even after dyno tuning which I assume was down to poor distribution ultimately.

Other things- The gen 3 cam profiles dont help carb induction....late intake valve opening events and minimal overlap are not carb friendly.....and its hard getting any supplier to step up to the plate and acknowledge what the actual ICL is on a lot of their products....where they install is often very different to the quoted recommended ICL.

The assumption seems to be its up to the customer to swap out the slugs and advance the cam....rather than be honest about the limely effects of a 114 install ICL.

I run a Carter 120 gph 7 psi fuel pump with 1/2" line - Ive had no starvation issues with A 800AVS, 830 Pro system Holey or dual Eddie 500s


Last thing.....if I took you for a ride on the street..you'd think I was crazy...the thing lights the tyres and runs a 3.8 0-60..... But at the track where the tyres don't spin to allow faster cylinder filling......the induction system is on the ragged edge of failure and performs average at best.


Stalling up makes it worse, as this reduces pump shot travel thus less fuel tip in.
 
On the subject if EFI....I know very little but could probably guess the following..

Fuel distribution would be vastly improved due to superior atomisation.

You have the benfits of computer controlled flow and timg..so its doubtful the bogging that occurs with carbs would occur.

The cam characteristics become less of an issue for the same reasons...the computer will ensure optimum timing and distribution.

However...a gold plated turd is still a turd.....and I think the short indirect runner platform of the Modman will still effect cylinder pressure and thus effect low/ mid torque and probably make the motor peakier.

It will make more power across the range than dual carbs......but not as much as the factory intake.

One thing I forgot to mention........my motor is still making power at 7000 rpm while efi cars with the same cam are all done by 6700......another indicator of how the torque band is effected by this style of intake.


On the subject of cold and hot starts...I dont run a choke..and am accustomed to pumping the throttle a couple of times when the motor is warm

Carbs arent perfect , Eddies dont like the heat.....and Im certain mine also suffers from a bit of fuel pooling on top of other things.....another reason Im changing to the dual plane dual quad.

You can only give the motor what it wants and what you're happy with.
 
The first stuff on the card is interesting.

As for the heat gun. I now understand what you are saying about the mod.

My 1 and 7 as well as 2 and 8 run cooler ! while in the garage. On the stands

Its -18 Celsius today . cold in Ontario Canada bro! I would be able to do any runs on the car until wheels and exhaust .
 
It may be that my divider helped the fuel distribution......Id do a back to back if I wasnt swapping it out.....
 
Rat Patrol said:
...
One thing I forgot to mention........my motor is still making power at 7000 rpm while efi cars with the same cam are all done by 6700......another indicator of how the torque band is effected by this style of intake....
Click to expand...

Did you do anything extra to your engine to be comfortable running it that high or do you even pull those kind of rpms on a normal basis? I've currently got my limiters set up around 6200-6300 (timing cut at 6200, fuel cut at 6300 as a backup). I've thought about bumping things up to 6500, but without some dyno evidence that it's still making power and general comfort feeling on spinning stock parts that fast I wasn't ready to pull the trigger. I've heard you get into the oil starvation issues if you go too high, I think closer to 7000 was the number I heard on that.
 
Map63Vette said:
Did you do anything extra to your engine to be comfortable running it that high or do you even pull those kind of rpms on a normal basis? I've currently got my limiters set up around 6200-6300 (timing cut at 6200, fuel cut at 6300 as a backup). I've thought about bumping things up to 6500, but without some dyno evidence that it's still making power and general comfort feeling on spinning stock parts that fast I wasn't ready to pull the trigger. I've heard you get into the oil starvation issues if you go too high, I think closer to 7000 was the number I heard on that.
Click to expand...
A modern hemi will suck a 6 qt pan dry roughly about 6500 give or take. It depends on how long the engine it at rpm. It is true so be carefull. I ran mine dry at 7500 before and learned first hand about this issue. Luckily only some very small damage! 9 quart pan now. No more issues.
 
Map63Vette said:
Did you do anything extra to your engine to be comfortable running it that high or do you even pull those kind of rpms on a normal basis? I've currently got my limiters set up around 6200-6300 (timing cut at 6200, fuel cut at 6300 as a backup). I've thought about bumping things up to 6500, but without some dyno evidence that it's still making power and general comfort feeling on spinning stock parts that fast I wasn't ready to pull the trigger. I've heard you get into the oil starvation issues if you go too high, I think closer to 7000 was the number I heard on that.
Click to expand...

I was told that above 7k the oil drain back becomes an issue - so I change regularly at 6900 at the track with no issues.

On the dyno the limiter was set at 7k...first couple of pulls we bounced the limiter but the curve was still climbing....but only slightly.

I put it down to the retarded onstallation of these Gen 3 cams combined with the intake.

How do I know the cams are retarded?

Two reasons - First...the can card provided with my inertia can states 'to be installed at 106 ICL' ....yet these cams actually install at 114 to avoid piston/valve clash...we degreed mine - and verified by Stu from Inertia.

2nd...Chris from Modern Muscle has also stated on this forum, that grnding these cam profiles on a retarded ICL is 'unavoidable'.....in order to achieve decent duration without p-v clash.

So single plane intake, short runners, retarded cam.....its not surprising.
 
Okay, I have the Milodon pan which I think is closer to 7+ quarts and a remote oil filter with a fairly large filter that might bump that 0.5 quarts. I still have no intentions of winding it that high on a regular basis, but if I felt like being a little cheeky at a stoplight or if I ever do make it to a test and tune night I might push it a bit. Still want to get it on a dyno before I make any decisions. No point spinning it that fast if it's not doing any good.
 
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