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Some of you may have seen my earlier post "353 rwhp, 383 rwtq, WTF".......

Anyways I think I got to the bottom of my problem with low RWHP. Basically with my current mods and based on looking at over 20 dyno charts of BPU-/BPU/BPU+ cars for comparison I fell I should be making 415 rwhp but I only put down 353.

I had a compression test done today and here are the results:

Cyl.
#1 140
2 130
3 140
4 135
5 130
6 130

Average = 134 psi
Normal Compression = 156
Minimum compression = 128

Mike at altered atmosphere said the norm was 150-165. Warren said about 150 is the norm.

Obviously something is wrong and I believe that since my compression is 15% lower than normal it would explain why I am lacking 60 more rwhp. Does everyone agree?

The next thng is what could be wrong?

Bad seals, piston rings, pistons, valve adjustment needed? I am going to do a leak down test ASAP and then hopefully use my extended warranty.

Has anyone ever seen/heard of this type of problem? I though the Supra engines were bullet proof?

Other things to note:

mobile 1 every 3K
51K miles
BPU+ (Greddy FMIC)
previous dyno on 94 pump gas
Profec A ( switching to an EVC-EZ) holds only 18 psi or so
Oil goes low 1 qt at oil change but I don't see smoke out of the exhaust.

Thanks for your help!nullnullThe next thng is what could be wrong?
 
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Engines are not idiot-proof tho. They need TLC and owners need common sense. Sounds like you need a wet/dry compression + leakdown test to determine if it's the rings or the valves that are leaking. Good luck. Look up post by Larry (SP) talking about rebuilding the stock bottom end to make it bulletproof for approx $3000. Good luck.
 

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Some gauges are not accurate at ALL, AMHIK. I'd try with another gauge and see how it is. At least they are all consistant, which is a good sign. Look at it this way, the less compression, the more boost you can run :)
 
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Originally posted by Grant:
<STRONG>Some gauges are not accurate at ALL, AMHIK. I'd try with another gauge and see how it is. At least they are all consistant, which is a good sign. Look at it this way, the less compression, the more boost you can run :)</STRONG>
I agree with Grant. I did a compression check with a couple of guys on my car over the weekend and #5 came back low. I was bummin. Anyway, I went out and purchased my own gauge and followed the instructions on MKIV.com. (my manuals are on the way) Your car should be at operating tempratures before taking any readings, there are also some sensors that you need to disconnect. Anyway, with my own gauges I was able to measure pretty much the same thing the dealer said they measured when I purchased my car. My car was abused and has 81K miles on it. The lowest number was 148psi and the highest was 155psi.

I paid $60.00 for my gauge and it was worth every penny :D

[ April 18, 2001: Message edited by: Melvin ]
 
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