LS2 120 RWHP loss
10-09-2007, 05:19 PM
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LS2 120 RWHP loss Hi,
I have an LS2 ( all mods in sig) Dynoed at 535 RWHP. After about 2 weeks or so I knowticed some power loss but wasn't sure because I don't drive it much. Maybe 2 or 3 times a month. brought it back to the dyno to find that it was down to 410 RWHP. the computer said that #6 spark plug was skipping. also the tune was rich. do you think it could be that the spark plugs are fowled or something?
I will be doing a compression test next weekend.
What else could it be?
HELP!!!!!!!
Al
I have an LS2 ( all mods in sig) Dynoed at 535 RWHP. After about 2 weeks or so I knowticed some power loss but wasn't sure because I don't drive it much. Maybe 2 or 3 times a month. brought it back to the dyno to find that it was down to 410 RWHP. the computer said that #6 spark plug was skipping. also the tune was rich. do you think it could be that the spark plugs are fowled or something?
I will be doing a compression test next weekend.
What else could it be?
HELP!!!!!!!
Al
10-09-2007, 05:45 PM
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Replace the spark plug and reduce the amount of flow at the fuel pump. Sometimes it takes a little while for an engine to get "Broke In," and the fuel pump could've just started for that very reason.
10-09-2007, 06:37 PM
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Do you realy think that one spark plug could cause the motor to loose 120 Hp?
What do you mean reduce the flow on the pump? it is dyno tuned to 11.5 AFR give or take approx .3
10-09-2007, 07:36 PM
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Pull the plugs first, that will let you know a lot. That said 120 HP is a lot to lose, sounds like a cylinder or 2 isnt firing.
And maybe a boost leak too.
And maybe a boost leak too.
10-09-2007, 10:14 PM
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But you bring up a valid point about the clutch slipping. no smells but it has a kevlar clutch and may not smell if it slipps, not sure.
The clutch has about 2500 - 3000 k on it should be ok
we did put it under load on the dyno and it was consistant so I will have to think about this one more
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10-10-2007, 10:34 AM
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check the plug wires and plugs. Ive had wires pop off the plug and believe it or not, one plug not firing will cause you to loose 100+ hp. think about it, you have 7 cylinders dragging one dead cylinder. 
10-10-2007, 11:49 AM
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Hi,
I have an LS2 ( all mods in sig) Dynoed at 535 RWHP. After about 2 weeks or so I knowticed some power loss but wasn't sure because I don't drive it much. Maybe 2 or 3 times a month. brought it back to the dyno to find that it was down to 410 RWHP. the computer said that #6 spark plug was skipping. also the tune was rich. do you think it could be that the spark plugs are fowled or something?
I will be doing a compression test next weekend.
What else could it be?
HELP!!!!!!!
Al
I have an LS2 ( all mods in sig) Dynoed at 535 RWHP. After about 2 weeks or so I knowticed some power loss but wasn't sure because I don't drive it much. Maybe 2 or 3 times a month. brought it back to the dyno to find that it was down to 410 RWHP. the computer said that #6 spark plug was skipping. also the tune was rich. do you think it could be that the spark plugs are fowled or something?
I will be doing a compression test next weekend.
What else could it be?
HELP!!!!!!!
Al
So if 2 plugs arent doing there job you can lose substantial power. Not only do you lose power production, but the other cyl now have more load to handle, so they become less efficient also.
Since they fire on occasion you are not getting the full loss, but it is a big loss no matter what.
Good luck!
10-10-2007, 12:39 PM
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Math lesson - 535hp/8 cyl = 67hp/cyl x 2= 134hp loss.
So if 2 plugs arent doing there job you can lose substantial power. Not only do you lose power production, but the other cyl now have more load to handle, so they become less efficient also.
Since they fire on occasion you are not getting the full loss, but it is a big loss no matter what.
Good luck!
So if 2 plugs arent doing there job you can lose substantial power. Not only do you lose power production, but the other cyl now have more load to handle, so they become less efficient also.
Since they fire on occasion you are not getting the full loss, but it is a big loss no matter what.
Good luck!
Yes I had figured this out, just didn't post it
10-10-2007, 01:02 PM
#18
Each cylinder is making approximately 78.75hp.
10-10-2007, 01:07 PM
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Can you explain this to me? I don't get the jump from RWHP to BHP. Are you talking 630*.85 = 535.5? and are you talking 630 BHP at the crank now.
Last edited by STKN1STGEAR; 10-10-2007 at 03:23 PM.
10-10-2007, 01:20 PM
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Forget all the stupid calculations, just have your plugs, wires, and coilpacks checked. To check the wires and packs all you really have to to to pull one wire off the plug when the engine is running and hold the end of the wire up to some metal on the motor, you should see the spark arc across the wire and jump to the engine. I would just go ahead and replace the plugs though.
If all the checks ok then do a compression test.
If all the checks ok then do a compression test.