Anyone notice a real difference in idle coolant temps from say 10-32*? I've always heard low timing at idle makes more heat. Any truth to this?

Current engine seems to idle smoothest around 12* and 13:1 which seems really low. (e85) 15-22* range is what I usually ran.

I found if I crank it way up to 32* at idle it cleans up a bit and I have to pull fuel. Seemed like maybe this idled slightly cooler but I could be full of it. Anyone have experiance with this?


Any suggestions?

Engine is a 370, 224/224 @ 113 .610 lift cam. Untouched 317 heads.

Thanks

 

At MBT so about 24-28* on a LS head.

 

you should be in mid-upper 20s at idle.

turn up the timing until your MAP peaks.

 

I run 30 degrees at idle on my 5.3L with the ASA cam. Adding timing made it idle smoother and picked up torque at just off idle, which is good since I have a stick car. It is true that less timing will run hotter. In fact, most OEM tunes have timing retard strategies to get the engine to operating temperature faster.

Andrew

 

Makes a big difference on forced induction first gen SBC from my experience. So I would agree with everyone else.

 

Since he posted about E85, do you think MBT would happen at the same timing range? Also, since alcohol burns cooler than gasoline, I'm curious as to what has prompted this discussion.

 

Thanks.

Gave 26* a shot. Sitting in traffic with this particular engine I'd see coolants creep up to 210ish on 90+* days. Which is know isn't horrible, but it takes longer to cool off if I want to make a pass with the temps up above 200. I'm was use to my LS stuff running around 190-195ish on hot days with this cooling system. The 370 has always run a little hotter. Seemed to hover around 200ish today waiting inline to get in the track for 15 minutes. So maybe it helped 10* or so... I'll play more and post back. Has about 50% coolant in it as well. I'll try ditching that for straight water and a little water wetter.

 

there is a very simple scientific way to tackle these sorts of questions.

Datalog with:
10*
20*
30*

Compare vacuum, idle speed, EGT, for some number of minutes.
Then adjust Air/fuel ratio and repeat the test for reasonable ratios (14+ usually)

You can do the same thing for fuel economy cruise situations:
data-log EGT, vacuum, Injector duty;
Increase or Decrease timing using 5* increments
Compare data-logs. You want the highest vacuum with the lowest injector duty and lowest EGT in most situations for cruising at normal speeds, you MUST USE CRUISE CONTROL. Higher speed cruising (100mph+) throw all this out the window and keep the air fuel reasonable near the low 14's to high 13's for safety (as you tip in at those speeds the engine is much more likely to lean misfire)

IMO Idle timing I tend to keep say 15-22*. Alot of engines have idle timing control which constantly jumps the timing around to help steady the idle, making it much less of an "ordeal" when deciding what number to actually put into the map. Some ECU will even over-ride the users input number for some static hard-wired starting value (apexi Power FC does this). The Cruise timing is much more important for keeping an engine cool than the idle timing; you should not be throwing off enough temp rise during idle to cause an issue. The engine BTU/joules output around idle is minimal compared to say, high RPM at WOT.

 

if you want to find out what your engine likes for fuel/spark at idle, try the following: Turn off Closed Loop, Idle Spark and IAC. Ignore your AFR as it is most likely skewed by the overlap of your cam. Adjust fuel for highest idle/ lowest MAP and do the same for spark. I would drop the MBT spark by about 5 degrees to give your Idle Spark some torque reserve for A/C, fans coming on etc.

Mike

 

My LQ9 with the LS6 cam has the identical tuning specs as yours: 12* and 13:1. Any more or less I lose vacuum and lose stability. Can't comment on engine temp...mine runs cool at idle. At speed is where I have an issue.

 

I would also do the timing based on map pressure but noticed after a given amount of advance map would change by small amounts so I would back it off when that happens. I believe stock idle timing is around 18 degrees so I find it hard to believe you would run less than that on anything with a cam since it's less efficient at idle you should be able to advance it more. I usually stay around 20-24 degrees on cammed stuff. FWIW.

 

I would never let any engine idle at 13:1. I am sure it would be fine with 14.5:1 or 14.8:1. Perhaps the O2 sensor is incorrect in idle region; in this case, tune by ear. Subtract fuel until the engine stumbles a bit then add some back. This should get you near 15's or 16's (the more stock the cam, the higher the a/f the engine will tolerate at idle generally).

Another problem is the injector on-time might be too low near idle speeds. If you can hold a 15:1 idle at 1000rpm but the engine dies when you cross into the 14's at 850rpm, the injectors might not be opening anymore intermittently. In this case you would need to lower fuel pressure or use a different injector, or higher idle speed, or play with the dead-time setting a bit (it might help).

I tuned an LSx with 1000cc injectors, and a 236/236 @ 0.050 cam, and it still idle'd plenty fine with 14.5:1 a/f ratio, although it has plenty of RPM with that duration you bet. Point is, you don't want to run ANY engine for extended periods with a 13:1 or similar, it will carbon everything up and generally coat the parts faster with that terrible thick black coating, gradually foul up the plugs, reduce quality of combustion, and since it coats the exhaust system the car will smell more/more often even when cruising lean (the 'foulness' of the frequent carbon coatings seems to stick to the insides of the exhaust)

 

If he's running e85, 14.7:1 is NOT what you shoot for.

 

I've respectfully disagreed with a number of your posts. At this point I am officially calling you a ******* retard. 13/1 AFR will absolutely not "carbon everything up".

 

^ lol I don't think kings ever tuned a turbo ls car. Go spread your wisdom and theories back on the dsm forums.

 

13:1 is terrible for any engine at idle. If you do not feel that way... that is your opinion. I would never let a customer take away an engine that idle'd at 13:1. It will surely cause the plugs to foul over time and reduce the quality of combustion. Guaranteed, any engine, every time. Just because it still runs doesn't mean it isn't getting filthy inside. Furthermore, you have no way to check or measure the amount of carbon filth created by the 13:1 condition for extended periods at idle... So where is your proof or math behind this theory that I am incorrect? I see nothing but useless words! Call me more names if it makes you feel better. that seems to be the way things go once people run out of other ideas, they start name calling and pointing out my bad grammz

 

You calling me out?" because I will start filling the thread with pics of videos of turbo cars I tuned

thats all I tune, and there are hundreds of engines out there idling around 14.5 and 14.9:1 that I took the extra time and care to ensure wouldn't wander into the 13's at idle. And the plugs come out lookin clean as they went in, the engines sound and smell great. And that is what matters to me.

 

So you're literally saying regardless of the combo and such things as cam overlap you always tune to 14.7? That basically shows you're an amateur and your tunes are as good as a mail order tune. Nice job.

 

Where does it say that?

My post says to always tune to the leanest air fuel ratio near 14.7:1 or 14.9:1 as possible, sometimes 15.1:1 but never 15.5+ and never 14.5 or less generally, sometimes you need a 14.4~ to smooth out loading up a compressor. I've never needed a 13:1 though.


Cam overlap has little to do with air/fuel ratio. Before you fly off the handle saying it does, consider that 1.225ms of fuel is still 1.225ms of fuel regardless of what camshaft you put into the engine. The wideband isn't going to read the same but the same exact amount of fuel still entered the engine, thus the a/f is identical from cam to cam if the MAP or MAF is "100%" accurate in both situations (even if it doesn't appear the same on the gauge) in theory. Also, It shouldn't be spilling out during overlap if you've phased the injector correctly to spray as the piston is descending with the intake valve open, post exhaust valve closure. And even then, if it did(spraying to a closed IV), losing a little bit is part of the game and you compensate for it by ear since the wideband isn't going to display properly.

We have 2 main goals at idle:
1. clean engine (oil) as possible
2. little fuel as possible (economy)

Together, with 1 & 2 we are reducing the engines temp rise output (energy leaking out of fuel $$$ and into the air around the engine and in the exhaust), keeping the insides cleaner (less carbon going in = less carbon sticking to surfaces (fuel is the carbon source), reducing fuel requirements as much as possible (always a good thing), and did I mention how it keeps the oil cleaner (less carbon byproduct contamination)

main idea:
Run two engines, one with 14.7 and one with 13:1 at idle for an extended period and compare them. The 13:1 engine will have notably fouler oil, and plugs, and more carbon contaminants partially combusted byproduct sticking to all surfaces.

You can see a similar effect clearly in practical applications by comparing two common engine scenarios, one run with a closed loop narrowband and one tuned by a pro using open loop at leaner air fuel ratios. The engine run with 15:1+ will have white/clean plugs (want a picture? I do this) and the one run with 14.7:1 narrowband will show tan/brown plugs (typical). With that in mind, think of what a 13:1 would give you!

 

yes, please do this. I think it would go a long way to establishing your credibility.

I don't mean this as a dig at you personally, but your posting pattern often makes me wonder if you are some sort of advanced AI that has read all sorts of tuning forums and collates the data into an indecipherable word salad intended to troll us.