Knock sensor problem solved
Thread Starter
Drifting
Joined: Jun 1999
Posts: 1,874
Likes: 1
From: Garden Grove CA
Knock sensor problem solved
Shortly after bolting everything up after three years of non-use I discovered that my knock sensors were going off and retarding the timing. The first question is always "is it real knock, or is it imagined knock. Since the knock spark retard was kicking in at idle, I was pretty confident it was imaginary knock - and so I went drag racing this last weekend even with the spark knock retard cutting back my power.
I was not especially looking forward to tracking down the culprit, but the solution ended up being quite easy. In my case it was a bad idler pulley for the serpentine belt. So if your knock sensors seem to be going off for no obvious reason you may want to see if the idler pulley bearing is shot.
Thomas
I was not especially looking forward to tracking down the culprit, but the solution ended up being quite easy. In my case it was a bad idler pulley for the serpentine belt. So if your knock sensors seem to be going off for no obvious reason you may want to see if the idler pulley bearing is shot.
Thomas
Thread Starter
Drifting
Joined: Jun 1999
Posts: 1,874
Likes: 1
From: Garden Grove CA
Re: Knock sensor problem solved (The Green Rocket)
Oh yeah, if you are working on an LT1/4 Vette, then you might as well pick up two replacement idler pulleys. The LT1/4 has one fixed position idler pulley and one that is on the belt tensioner.
Thomas
Thomas
Thread Starter
Drifting
Joined: Jun 1999
Posts: 1,874
Likes: 1
From: Garden Grove CA
Re: Knock sensor problem solved (dizwiz24)
Actually dizwiz24, I expect to have it in excess of 370 rwhp very shortly - and with a much fatter midrange. One of the things that had bugged me in the past was computer tuning, since my '95 uses flash memory instead of the chip like yours - this left me with various tuners who made me programs based on their best guesses. I now have LT1Edit, which allows me to use my own laptop to make changes almost on the fly. In two weeks I have two hours of chassis dyno time booked so that I can dial in my combo like I have never been able to before, especially since the dyno facility has a wide band o2 sensor that I am having an auxillary bung welded in just forward of my cats for more accurate tuning feedback
My combo is suprisingly like yours. It reads as follows:
1) Stock '95 bottom end
2) Pro ported LT1 heads, with a 185 cc intake port (was 169 cc's stock) they flow 257 cfm @ .550 lift on the bad ports, and 262 cfm on the good ports, exhaust flows ~ 202 cfm @ .550, use undercut intake and exhaust valves, use LT4 springs, titanium retainers.
3) Intake manifold has been ported to be ~ 1/8" smaller all the way around than the cylinder head intake port to deal with low speed reversion issues. Throttle bores enlarged for possible future use of a 58 mm throttle body, currently runs a TPIS 52 mm throttle body.
4) Complete LT4 HotCam kit, also runs the HD 1/2" timing set, installed straight up.
5) Shorty Watson headers (not available anymore I understand). Most of the other shorty headers are not better than the factory manifolds in my opinion - too many have the wrong port shape or collector design problems that actually decrease exhaust airflow.
6) Ignition is stock opti (resist all temptation to combine a "box" with an opti, they don't work), coil is a low impedence MSD which is like the factory '96 coil but with the proper connectors for the '95 and earlier LT1, use Taylor Spiro Pro 10.4 mm ignition wires, run Champion RS14YC6 plugs gapped at ~ .055
7) Exhaust is stock, even uses factory mufflers. I welded in cut outs with removeable plates just aft of the resonator for track use. On the dyno uncapped they are worth ~ 10 hp across the board.
8) Ford Motorsports 30# injectors. This is the right size for this power level in a sequential fire fuel injection, I'm not sure what would be the right size for your batch fire fuel injection.
9) I use an American Performance International ram air kit (through the radiator upper shroud), removed the MAF screens, smooth ducts to replace factory accordian ducts between the air cleaner MAF and throttle body.
I think that is everything except for computer tuning. It will rev past 7,000 rpm - I found that out by mistake (and sucked a valve in the process) - a tuner had set my rev limiter at 7,240 rpm. So now I watch it when doing burnouts.
My previous 4 dyno visits were all between 364 to 367 rwhp. Max rpm that I allowed on the dyno was 6,200 rpm - power was still climbing at that point, that was just my comfort level rpm wise on the dyno.
My past best 1/4 mile was a traction limited 12.74 e.t. at 114.35 mph. I recently ran it at a higher altitude track where it ran a (corrected for altitude) 12.8 e.t. at 111 mph on regular street tires - and this was with the aformentioned knock sensor problem that was cutting advance back to ~ 25 degrees and hurting the power level. This is with shifts at about 6,500 rpm. I expect that with the tuning and traction issues addressed by the time of the next West Coast Corvette Challenge that it will run in the very low 12's at ~ 115 mph.
Yours is performing below what I expect it would, and probably less than what you expected, maybe we should start another thread to address your combo and where the horsepower is hiding, I'll bet it would help some others to see what is holding your car back.
Thomas
My combo is suprisingly like yours. It reads as follows:
1) Stock '95 bottom end
2) Pro ported LT1 heads, with a 185 cc intake port (was 169 cc's stock) they flow 257 cfm @ .550 lift on the bad ports, and 262 cfm on the good ports, exhaust flows ~ 202 cfm @ .550, use undercut intake and exhaust valves, use LT4 springs, titanium retainers.
3) Intake manifold has been ported to be ~ 1/8" smaller all the way around than the cylinder head intake port to deal with low speed reversion issues. Throttle bores enlarged for possible future use of a 58 mm throttle body, currently runs a TPIS 52 mm throttle body.
4) Complete LT4 HotCam kit, also runs the HD 1/2" timing set, installed straight up.
5) Shorty Watson headers (not available anymore I understand). Most of the other shorty headers are not better than the factory manifolds in my opinion - too many have the wrong port shape or collector design problems that actually decrease exhaust airflow.
6) Ignition is stock opti (resist all temptation to combine a "box" with an opti, they don't work), coil is a low impedence MSD which is like the factory '96 coil but with the proper connectors for the '95 and earlier LT1, use Taylor Spiro Pro 10.4 mm ignition wires, run Champion RS14YC6 plugs gapped at ~ .055
7) Exhaust is stock, even uses factory mufflers. I welded in cut outs with removeable plates just aft of the resonator for track use. On the dyno uncapped they are worth ~ 10 hp across the board.
8) Ford Motorsports 30# injectors. This is the right size for this power level in a sequential fire fuel injection, I'm not sure what would be the right size for your batch fire fuel injection.
9) I use an American Performance International ram air kit (through the radiator upper shroud), removed the MAF screens, smooth ducts to replace factory accordian ducts between the air cleaner MAF and throttle body.
I think that is everything except for computer tuning. It will rev past 7,000 rpm - I found that out by mistake (and sucked a valve in the process) - a tuner had set my rev limiter at 7,240 rpm. So now I watch it when doing burnouts.
My previous 4 dyno visits were all between 364 to 367 rwhp. Max rpm that I allowed on the dyno was 6,200 rpm - power was still climbing at that point, that was just my comfort level rpm wise on the dyno.
My past best 1/4 mile was a traction limited 12.74 e.t. at 114.35 mph. I recently ran it at a higher altitude track where it ran a (corrected for altitude) 12.8 e.t. at 111 mph on regular street tires - and this was with the aformentioned knock sensor problem that was cutting advance back to ~ 25 degrees and hurting the power level. This is with shifts at about 6,500 rpm. I expect that with the tuning and traction issues addressed by the time of the next West Coast Corvette Challenge that it will run in the very low 12's at ~ 115 mph.
Yours is performing below what I expect it would, and probably less than what you expected, maybe we should start another thread to address your combo and where the horsepower is hiding, I'll bet it would help some others to see what is holding your car back.
Thomas
