The pathfinder sounds impressive. I missed a newer Express van with low miles and an 8.1 two weeks ago. I did not have the time to drive 300 miles before someone else grabbed it.
I was told not to waist my time, but I was curious to see for myself.
I got a cheap Jet Stage 1 chip to look at used. Its for a 1995 350 4l60e so I put it in. My chip with only revised shift points in a few gears was much more noticeable when towing. So I compared it to the stock truck bin to see the difference.
Main Spark vs Map Table was bumped by 1.1-3.2 degrees. This is supposed to be for a stock engine, but a lot of the changes were at 4400-6000 so not even noticeable as the engine never runs that high.
They bumped the fuel cut off from 98 to 115 mph, the only way my van will ever see that, is if it falls off a cliff.
The main fuel table was increased in almost the same areas they bumped the timing. Probably to combat detonation by making the engine very rich.
I cant believe, companies get away with selling this for $150 and up. Mine cost almost nothing so it was almost worth it just for the education on what not to do.
Last edited by donf; 06-16-2018 at 03:40 PM.
Hi Don. I was pretty active tuning my stock 1995 K1500 several years ago. My tuning threads are here:
engine
http://www.gearhead-efi.com/Fuel-Inj...uning-Autoprom
trans
http://www.gearhead-efi.com/Fuel-Inj...E-tuning-in-0D
header install
http://www.gearhead-efi.com/Fuel-Inj...header-install
I've attached my bin if you want to have a look at it. Truck has nearly 180,000 miles on it now. Same stock LO5 and 4L60e.
1995 K1500, Stock LO5, 4L60e, 3.73 gears, 265/75-16 tires, L&L Products Ultra-flow headers into 2-1/2" Y-pipe and 3" single exhaust
I read a Hypertech I found in a 92 GM van once. For $2 at the wrecking yard. All they did is target a leaner PE mixture and increase the VE table and spark map in the 80+ KPA range. I tried it and WOT it actually ran very well but no changes to anything that would effect emmisions.
Thank you I will take a look! I am sure there is some good stuff in there. Billy Graves has already helped me too with some trans help.
No PE changes in the Jet chip. I did not bother to dyno it. I took it out after one trip pulling the trailer and dyno to the track. A lot of the changes were in the rpm ranges well past the limits of a stock 350 tbi. Every change over the stock chip is shown in this screen shot.
Last edited by donf; 06-17-2018 at 04:47 PM.
They were probably just cleaning up the non calibrated GM mapping in that area. From the files I have seen over the fuel kill they put a flat lined timing and VE map from GM.
Where I see the best gains from tuning TBI chips is in the off-idle to 3,000 rpm range. The factory often used negative or very low advance values under load. Most of the engines I have played with like 8-10° of advance by 1,000 rpm, 20° by 2,400 and full advance of 26-28° by 3,600 rpm. That is only possible if they are not tunning lean like many do in factory form. I have gained 20-30 ft/lbs at the wheels running timing like that and a WOT air/fuel ratio of 12:1 in that RPM range. Up around peak HP in the 3,600+ rpm range taper off the fuel to about 12.6:1. Watch for knock retard with the trailer in tow and adjust accordingly until it goes away, then pull 2° more for safety. If running 91+ you can actually find yourself advancing the timing past the point of losing power without running into detonation.
This is the timing map I had in my 7730 TPI ECM that was running a stock TPI intake on a 1-ton 8.8:1 350 TBI engine with a LT1 F-car cam in my 1983 G20 van. PE spark is high at the top rpm because the TPI runners and swirl port heads are choking off the airflow by that RPM. More timing kept the power from falling off quite as noticeably. It had good power to ~5,200 rpm.
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