×

Sale ends todayGet 30% off any course (excluding packages)

Ends in --- --- ---

Anyone want to lend a hand?

General Tuning Discussion

Forum Posts

Courses

Blog

Tech Articles

Discuss all things tuning in this section. News, products, problems and results. 

= Resolved threads

Author
680 Views

Hey all, let's get the specifics out of the way first. 1999 4.8, sloppy stage 2 cam, long tube headers with 1 3/4" primaries, hand port matched heads, LS2 intake manifold with factory truck throttle body(I have enlarged the hole in the blade that was already there from GM in an attempt to get my IAC counts down below 190), 35lb flex fuel injectors. Engine management is by way of the factory GM pcm from the 1999 truck using HP Tuners, running OL/SD. Transmission is the 4L60E with a Revmax converter that is entirely too tight for my application (I know that with my cam, I need around 3000stall, and that is what I ordered but after installing it I found that I would have been better off going with the factory converter as it has pretty much no stall. It tries to push through my brakes, footbrake stall is all of 1200-1400rpm. I am very disappointed with revmax at this point as they refuse to restall it[telling me they CAN'T restall this one], and also the point that they told me this converter would be a good fit for my car). The vehicle it is in is a 2001 Lexus IS300(curb weight of 3200lbs, as quoted by Toyota).

I have been working on this tune for a good while now and am struggling to refine it. I swapped from the truck intake to the LS2 intake recently and that is when my problems seemed to compound and it seems as everything I am doing to try and clean it up is only making it worse. My bigger issue out of all of them seems to be my base running airflow is very high. In the map the two are "in gear" and "park/neutral", the "in gear" values are pretty much twice what the "park" values are, although I'm assuming that is a product of my VERY tight converter loading the engine at idle in gear. My concern tho is that it seems to change from one drive to the next, one time acting like there is too much air and the next time acting as if there isn't enough. Every once in a while when I start it, it revs pretty high until startup airflow decays, then other times it starts up excellent but then has a rev flare once startup airflow decays, then other times it starts up and idles perfect. I have no issues with hanging idle or dipping too low and stalling, although my stit sometimes are all over the place, changing from drive to drive, going as high as -7.5g/s, but if I take that much out, then it wont stay running. I have searched several times for vacuum leaks using ether and carb cleaner and have found none. Another issue is a slight rev flare when shifting from gear to park. Then there is the issue of inconsistent AFR's. It isn't real bad, and I attribute it to the fact that I don't have the intake tube on yet so I have the IAT sensor just sitting up in the corner of the engine bay(no hood as of right now either), but I'm not sure if that is the cause as I've also been struggling a bit getting my ve map dialed in(due to the inconsistencies??). I have logged my idle airflow and dynamic airflow from cold(with the idle trims turned off) and input the values into my tune but it pretty much renders it not drivable unless I go back and add a bit to the p/n portion and a very significant amount to the in gear portion. I seem to be having a bit of an issue with AFR's during throttle transistions.

There are some other little refinements that could be fixed but I feel that if I can get this other stuff taken care of, the rest will fall in line. If anyone would be willing to take a look at my tune and a log to see if something jumps out at them, I would appreciate it greatly!

It also may be need to know info that I live at an elevation of 5000' and higher.

Attached Files

Can't view your file at the moment as I'm on my phone but did you keep the same throttle body when you swapped inlets? Or change to a bigger one at the same time?

How big is the hole in the throttle blade now?

Can you run a smoke test to look for any potential vac leaks?

Ben, I kept the same throttle body that was on the truck manifold.

I can't remember the exact size I went to but i only went up a few drill sizes from the one that was in it from factory.

I don't have the ability right now to do a smoke test, although I am going to look into getting whatever I may need to do that this week.

I feel like I may have found the cure to SOME of my problems. When I swapped to the LS2 intake, I went from a vacuum referenced return fuel system to a an AEM regulator with a return, but AM NOT running the vacuum reference. I input injector data for a vacuum reference, IE, flat lined injector flow rate vs kpa. I need to go find the flow rate from the later return-less fuel system (05 and later if I am remembering right).

Yeah, not having the vac line attached will throw that out of whack. Have you tried just hooking a vac line to the reg? Even just for testing purposes? Also have you verified that base pressure is it 4 bar?

Ben, I verify the fuel pressure with the gauge that is on the regulator itself, sshows a very consistent 52psi. I have not tried to hook up the vac line. I just went and found the flow vs kpa from an 05 L59(flex fuel 5.3). It seems to be more consistent now, but now I'm working on getting the ve back in line. I have taken a TON of air out of my base running airflow and it seems to be running and idling MUCH better, but it dips real low going into gear and at lights. It hasn't died at all tho and it is even showing that I need to pull more air out.

Have you done the russk idle learning for your airflow? Might be a good place to start if you haven't already.

Providing the intake side is sound; it does sound like the converter is pulling the revs down, make sure the trans is full and monitor the trans temp. ATF viscosity is pretty sensitive to temperature and we usually see around 100ml volume gain for every 10degC from about 50degC.

there is quite a lot involved in selecting the correct converter stall speed too and it is particularly sensitive to idle torque and light load transients. Changing the air flow characteristics by porting heads, fitting cams or changing compression ratio tends to have negative effects on idle/low load torque and this will require a higher converter slip or stall speed paying attention to the torque curve of the engine to ensuring that stall speed is lower than peak torque etc.

We usually reply within 12hrs (often sooner)

Need Help?

Need help choosing a course?

Experiencing website difficulties?

Or need to contact us for any other reason?