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Old 11-19-2019, 11:51 PM   #16
GrannySShifting
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Default Re: Compression causing power loss?

Quote:
Originally Posted by 68fastbak View Post
Why so much gap?? What makes you think you need .055?

How does the car run on the street? Have u track tested it yet? With a big stall it will read low on the dyno but that doesnít mean anything , Iíve seen cars with low dyno numbers run a lot faster on the track than cars making a lot more power on the dyno with stock converters or manual trans .I wouldnít get too caught up in Dyno numbers. I would put a new set of plugs in it gapped at 35 and take it down the track a few times ,you may be surprised
This is not a distributor with a 40 year old coil, its coil per cylinder capable of lighting off 1000+ hp on methanol. The plugs are at .055 because that how they come, and how they are from factory in their 650hp engines.

I guess people telling him to get a wideband cant read the part where he posted a picture of dyno WITH wideband? Dynojets arent perfect but I can tell you its underpowered by some amount for certain
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Old 11-20-2019, 12:13 AM   #17
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Default Re: Compression causing power loss?

The engine combination is off.
A 4000 stall is way too low. It'll be even lazier with the 4L80 behind it.
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Old 11-20-2019, 12:35 AM   #18
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Default Re: Compression causing power loss?

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Originally Posted by VENGNCE View Post
The engine combination is off.
A 4000 stall is way too low. It'll be even lazier with the 4L80 behind it.
Its likely a 4000 stall in name only, sitting behind a stock or mild cam engine. Pretty typical. If you look at his datalog looks like it flashes near 6000 rpm and falls back to higher than that
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Old 11-20-2019, 01:03 AM   #19
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Default Re: Compression causing power loss?

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Originally Posted by GrannySShifting View Post
This is not a distributor with a 40 year old coil, its coil per cylinder capable of lighting off 1000+ hp on methanol. The plugs are at .055 because that how they come, and how they are from factory in their 650hp engines.

I guess people telling him to get a wideband cant read the part where he posted a picture of dyno WITH wideband? Dynojets arent perfect but I can tell you its underpowered by some amount for certain
What plugs come from the factory with 55 gap? Why would you need that much gap? Every LS I ever saw came with less gap from the factory , and they are all coil at the plug, I have a 650 hp sbc and 600 hp ls on nitrous and both are gapped to 35 (nitrous ls even less)and both rev clean to 7000.I think itís a good idea to atleast try a little less gap and see what happens ,It takes 20 minutes to swap out plugs and that is probably the fastest and cheapest thing he can do at this point. More gap equals more resistance and is not needed ,Especially with more compression ,rpm,or forced induction/nitrous.I donít see any benefit in it.
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Old 11-20-2019, 02:44 AM   #20
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Default Re: Compression causing power loss?

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Originally Posted by 68fastbak View Post
What plugs come from the factory with 55 gap? Why would you need that much gap? Every LS I ever saw came with less gap from the factory , and they are all coil at the plug, I have a 650 hp sbc and 600 hp ls on nitrous and both are gapped to 35 (nitrous ls even less)and both rev clean to 7000.I think itís a good idea to atleast try a little less gap and see what happens ,It takes 20 minutes to swap out plugs and that is probably the fastest and cheapest thing he can do at this point. More gap equals more resistance and is not needed ,Especially with more compression ,rpm,or forced induction/nitrous.I donít see any benefit in it.
Dont know how many youve seen, but out of the thousands I have worked on, they all came from factory with that gap. NGK TR55 is stock replacement plug

https://www.sparkplugs.com/product.aspx?zpid=10160

Gap has nothing to do with it. I get 12:1 400" engines in all the time with TR55s in them, while I dont like the plug for that and swap it for something colder, they arent 80 40 or even 20 hp down because of it.
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Old 11-20-2019, 03:29 AM   #21
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Default Re: Compression causing power loss?

It's not the plug gap losing him power. GrannyShifting is right. I and most others been running TR55's in ls's with the gap they arrive with since the year 2000.

The headers aren't too big.

Delayed start is interesting. I had that and found 2 of my ignition wires weren't clicked into the coils properly. Are all the wires clicked into the coils 2 clicks? You must hear/feel 2 clicks. Some of the wires these days are made like crap and the outside of the wire where they crimp it goes deformed and the wires don't click into the coils properly. Like two of my latest purchased MSD wires i had to put crazy pressure on them to get the second click.. so much that i had to swap those wires to the front cylinders to be able to put that much pressure on them to get them to click in properly. Never had that issue with MSD wires before. In fact the reason i always liked MSD wires was how they fit. Now, not so much.

Little things like that can catch you out. The 4th gen engine bay doesn't help things.
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Old 11-20-2019, 10:04 AM   #22
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Default Re: Compression causing power loss?

Quote:
Originally Posted by GrannySShifting View Post
You dont. He did show wideband readings in dyno graph though. Guy needs to get a competent tuner behind this program, we know where and how to look for issues.

You cant say its TOO lean, cars like different things. 427 I did would go to 13.4:1 and be fine never knock, but it also didnt make any more power than 12.6:1 so thats where I ran it to give it cushion to play with timing

11:1 is not problem. might like more but its not losing 60.

The plugs are not the problem per se, a TR55 is a stock plug and they jump gap just fine. It is too hot of a heat range however and under load isnt a good idea. Inertia load on a dynojet aint much and wont hurt it

If you had coil problems I find that odd, Ive replaced maybe 3 oem coils due to failure. We have no ignition issues under 1100hp on factory stuff, no reason you should have to tighten gaps like that unless you have something wrong like voltage feed to them

2" headers are not hurting power appreciably on this and it prob prefers it when its right. Thats a good bit of cam for those big heads, this thing should make 550 to the tires on accident and peak at 7000rpm at least unless the valvetrain is unhappy.

Just because it says .660" lift springs and your cam lift is under that, doesnt mean it is adequate to control it. We take springs like that off and put single springs with max lift of .620" on some setups and turn an extra 1000rpm at times. Its all specific combination. How heavy is your intake valve? Youve done all you can do with that spring though shimmed to within .050" from bind so thats good

Your running a .030 head gasket how far out hole is piston? Thats too tight for 99% of LS engines I see, piston will hit head because they are usually .008" out of the hole

Its down a cylinders worth of power
Current gasket is .040 cometic. Block has been decked and sits right at 9.24. Its an iron block so I don't have any of the thermal expansion that the aluminum blocks have. My pistons are literally right at deck height at tdc (measured individually after machining) so at operating I am probably just a thousandth or two out of the hole from piston growth.

The plug range I can see is a consensus here. I am thinking I will bump to a TR6 and narrow the gap slightly into the .04-.05 range to see what happens.

The coils were original 99's with well over 200K miles on them. I was having slight backfiring issues at idle when adjusting primary and secondaries to even idle air distribution into the runners. I swapped my coils out for coils on my dads sierra and the backfiring dissapeared. I swapped my coils back on after a full cool down and IR gunned each cylinder and found 3 were noticeably colder than the others as it went up to temp. To confirm I moved plugs/wires/coils around and the problems followed the coils. I replaced them all with a new set of d585 delcos and all the issues went away.

I agree that 11:1 shouldn't cause this much issue, but I believe getting anywhere closer to 12:1 is only going to help this setup.

I also agree with the springs. While these are advertised for .660 lift and I was pointed towards these springs, the more I look into them they may not be capable of keeping the weight of these valves/pushrods in check in the upper rpms. Float would account for a great deal of power loss if this is an issue. Intake/exhaust valves are stock ls3's.


Quote:
Originally Posted by tblentrprz View Post
I would run gap no more than .040" Need to get a handle on tune - fuel and timing. Install WB02 or get real good at reading plugs (which means you can't drive around on em and get any real data) Maybe temp IR gun might locate problem cylinder after a quick pull and shut down.
Problem coils were found using IR gun, mentioned above. I really do need to get my own wideband in and going to see any of whats going on currently, I have a Ballenger AFR500 sitting on my desk now, but I have to wait until I travel back to my parents place to tig a bung in to the exhaust.

Quote:
Originally Posted by 68fastbak View Post
Why so much gap?? What makes you think you need .055?

How does the car run on the street? Have u track tested it yet? With a big stall it will read low on the dyno but that doesn’t mean anything , I’ve seen cars with low dyno numbers run a lot faster on the track than cars making a lot more power on the dyno with stock converters or manual trans .I wouldn’t get too caught up in Dyno numbers. I would put a new set of plugs in it gapped at 35 and take it down the track a few times ,you may be surprised
The car runs decently on the street. It does seem to have some hesitation when quickly pinned to wot, and it also has a bit of hesitation when transitioning from 'coasting' in OD to getting back on the gas, even slightly. I believe that the OD to positive pedal position is probably just due to the cam, but I am sure I could get it better mannered once I get everything else right.

Car unfortunately has not been tracked yet, I know big stalls are absolute heartbreakers on the dyno, but I should be seeing at least 500whp on a dynojet, it definitely doesn't feel like a 10 second car on the street. Its for sure hurting somewhere, like I said, it ran better with a tiny cam, shit heads, and a stock intake.

Quote:
Originally Posted by VENGNCE View Post
The engine combination is off.
A 4000 stall is way too low. It'll be even lazier with the 4L80 behind it.
4000 stall behind a stock ls1/6, its flashing considerably higher behind my setup. With the 4l80 ill be running a billet triple disk stalled 'higher', I know the car wants high 4 low 5 range. This car sees considerable street duty, so I will stall it slightly lower than track optimal, but itll still be high.

Quote:
Originally Posted by GrannySShifting View Post
Its likely a 4000 stall in name only, sitting behind a stock or mild cam engine. Pretty typical. If you look at his datalog looks like it flashes near 6000 rpm and falls back to higher than that
Exactly.

Quote:
Originally Posted by 68fastbak View Post
What plugs come from the factory with 55 gap? Why would you need that much gap? Every LS I ever saw came with less gap from the factory , and they are all coil at the plug, I have a 650 hp sbc and 600 hp ls on nitrous and both are gapped to 35 (nitrous ls even less)and both rev clean to 7000.I think it’s a good idea to atleast try a little less gap and see what happens ,It takes 20 minutes to swap out plugs and that is probably the fastest and cheapest thing he can do at this point. More gap equals more resistance and is not needed ,Especially with more compression ,rpm,or forced induction/nitrous.I don’t see any benefit in it.
TR6's with a smaller gap is going to be my first change. But llike others have said. Stock plug gap for ls1/6 is .055 on this heat range plug.

Quote:
Originally Posted by Launch View Post
It's not the plug gap losing him power. GrannyShifting is right. I and most others been running TR55's in ls's with the gap they arrive with since the year 2000.

The headers aren't too big.

Delayed start is interesting. I had that and found 2 of my ignition wires weren't clicked into the coils properly. Are all the wires clicked into the coils 2 clicks? You must hear/feel 2 clicks. Some of the wires these days are made like crap and the outside of the wire where they crimp it goes deformed and the wires don't click into the coils properly. Like two of my latest purchased MSD wires i had to put crazy pressure on them to get the second click.. so much that i had to swap those wires to the front cylinders to be able to put that much pressure on them to get them to click in properly. Never had that issue with MSD wires before. In fact the reason i always liked MSD wires was how they fit. Now, not so much.

Little things like that can catch you out. The 4th gen engine bay doesn't help things.
Ill take another look, I am sure that they are all in there correctly but it never hurts to check stuff thats free. I'll make sure its all perfectly seated when I swap out the plugs.

Last edited by Gtoproject; 11-20-2019 at 10:05 AM.
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Old 11-20-2019, 12:35 PM   #23
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Default Re: Compression causing power loss?

Make sure the piston isn't hitting the head with that .030 gasket. I've seen an engine that was a dog because of it. You might be able to see shadows on the piston with a borescope. Also, did not see what timing you were running. I have i similar combo 376 ls3 239/257 cam 11.5:1 makes peak power @7600 and carries to 8000. Mine doesnt seem to be very timing sensitive 27-31 degrees all make within 2hp. Thats on E85 though.
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Old 11-22-2019, 12:29 PM   #24
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Default Re: Compression causing power loss?

Quote:
Originally Posted by badfarmtruck View Post
Make sure the piston isn't hitting the head with that .030 gasket. I've seen an engine that was a dog because of it. You might be able to see shadows on the piston with a borescope. Also, did not see what timing you were running. I have i similar combo 376 ls3 239/257 cam 11.5:1 makes peak power @7600 and carries to 8000. Mine doesnt seem to be very timing sensitive 27-31 degrees all make within 2hp. Thats on E85 though.

I am currently running a .040 gasket and I doubt that they are touching, but I will take a look down in the cylinders when the plugs are out just to be sure. Timing was added and added on the dyno with no net change, currently it is sitting at 28*.
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