Spark Plugs and Compression, how does it look?

[HustlerTalon]

Just wondering if these spark plugs look alright...They are BPR7ES which I just took off the car after 1300 break in miles.

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I was adviced to swap over to BR7ES instead of BPR7ES and was wondering what the difference was? Visually they look different, but I was wondering if there were any performance differences?


One last thing, I did the Motoman break in procedure and currently have a little over 1300 miles on the motor (3 oil changes) and today I decided to do a compression test and it came out to be 155psi across the board. I have the 8.5:1 ross pistons and was wondering if the compression #'s I got were good or bad?

 

[Bmxr152]

I had about 156-169-165-171 or something like that at about 1,100 miles. Its supposed to be around 175psi across the board though. Oh and i had wesico 8.3.1 pistons if it makes a diffrence.

 

[JayRolla]

With that compression you should be hitting at least 175 accross the board.

 

[HustlerTalon]

I had about 156-169-165-171 or something like that at about 1,100 miles. Its supposed to be around 175psi across the board though. Oh and i had wesico 8.3.1 pistons if it makes a diffrence.

Those numbers don't look too good man. There is a 15psi difference between the first and last one. At least mine were even across the board.

I just want to be sure that 155 across the board is not bad since the motor only has 1300 miles. I guess I shouldn't have taken it to the track after only 300 miles

 

[Quasimondo]

I was adviced to swap over to BR7ES instead of BPR7ES and was wondering what the difference was? Visually they look different, but I was wondering if there were any performance differences?


One last thing, I did the Motoman break in procedure and currently have a little over 1300 miles on the motor (3 oil changes) and today I decided to do a compression test and it came out to be 155psi across the board. I have the 8.5:1 ross pistons and was wondering if the compression #'s I got were good or bad?

The difference between BR7ES and BPR7ES is in the design of the plug itself, which you've already noticed. The 'P' indicates that it is a projecting nose electrode design. The non-projecting nose BR7ES don't have the electrode protruding as much and are intended for use in high-compression engines with raised cylinder domes. They can't use a projector style plug because they'll probably punch a hole in the piston. There is some question about whether a non-projector plug will place the spark in the optimum position, but aside from that, there is no other difference. You shouldn't need to switch to BR8ES.

As for compression numbers, my personal preference is to have consistent numbers across all four cylinders, unless the compression test readings are abnormally low. If you're still unsure about your compression numbers, perform a leakdown test to see if you're something isn't sealing right. Keep in mind that if you're using an aftermarket headgasket, it may be thicker than stock, which may affect your compression ratio.

BTW, did you test with the throttle open? It's an easily overlooked step that skewers your compression test results.

 

[HustlerTalon]

BTW, did you test with the throttle open? It's an easily overlooked step that skewers your compression test results.

Throttle was closed. Is it supposed to be opened???

 

[DiamondStarAwd]

When I installed bp7es in my old 1g awd it would not idle. The idle would jump between 1k-2k constanly. Put the old plugs in it was fine. Bought a set of bpr7es and car was fine.

 

[DiamondStarAwd]

Throttle was closed. Is it supposed to be opened???

Ive seen numbers jumping 10-15 in cylinders

 

[HustlerTalon]

but is the throttle supposed to be opened or closed when I do the compression test?

 

[1993TalonTsiAWD]

Throttle should be wide open. Also car needs to be at operating temperature. If it's not your readings could also be way off. One big issue is that if your engine has aftermarket pistons (ross,wisco,etc..) than the piston to wall clearance is a little bigger. If the engine isn't warmed up there will be quite some blow by, more than normal. I have had 130-150 on a cold engine. On a warmed up engine 155-170. Also make sure your using the same number of cranks per cylinder or you could also get bad readings.

Derek

 

[spyderturbo007]

http://www.dsmgrrrl.com/FAQs/compression.htm

 

[Soup Can]

eh anything over 5 cranks is fine...most pressure gauges have a max hold feature that puts the needles at the max value it sees...since we have a 4 cycle engine anything over 4cranks will just go out the exhaust valves anyways...biggy is to make sure the car is warm when done...your numbers are even which is a great thing...sometimes rings take a little while to "set" to the block so dont worry about the low readings just yet...id do it again after you turn 2K and see what the numbers look like...they should go up a little...