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Discussion Starter · #1 ·
Hello to all. I have a Mini me headswap with a 3stage vtec head and Jdm non vtec obd2 bottom. Tuning was done with a p28 ecu with a relay to fire the first vtec while the second fired by the ecu at 4500. While the car ran well I just think am not getting enough mpg between 1000-3k rpm.
I am also surprised that my compression test show all cylinders at 125. Anyone with experience with this type of project please assist.
 

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Premium Member
'92 CX Twincharged D
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758 Posts
Ya I have a d15z7 head (3stg vtec) head on a d16a6 block in my 1g Integra.
I get 37mpg in town, mid 30's on highway.
I use a WB o2 output to ecu this help tremendously.
The 3rd stg I'd run it at 4.8k or higher to 5.2k
Then tune the fuel cells on map on highway cruise 15.5 to 17. AFR whatever your engine likes, with a little ign advance.
If vtec high lobe is active while at high cruise speed then the ecu add abit more fuel and kill your mpg.
Move vtec high lop activation to above 4.8k or even as high as 5.2k will save ya lot of fuel.
Also driving the car in 5th in town once you are at cruise speed of 25 or higher will also improve the intown mpg.

ALso adjusting the nut behind the helps a lot.... That being you
 

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Discussion Starter · #3 ·
Cruising speed is about 3k to 4k. Do you think I need rings? Is 125 across all four cylinder normal. Can it be that I lost compression on all four cylinder.
 

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Meat Popsicle
91 CRX Si
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Cruising speed is about 3k to 4k. Do you think I need rings? Is 125 across all four cylinder normal. Can it be that I lost compression on all four cylinder.
Doesn’t sound like an issue at all. It’s only a concern if there’s a large variance between cylinders.

If you really want to gauge the condition of the rings, use a cylinder leakage tester when the engine is hot.
 

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Discussion Starter · #5 ·
Tell me a little about the leak down test. I also have a miss every 20s or so when I idle. I drove a full stock 3 stage vtec engine and it ran from fumes and still had a lot of power.
 

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Sloppy Jalopy
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While the car ran well I just think am not getting enough mpg between 1000-3k rpm.
I am also surprised that my compression test show all cylinders at 125
maybe your cam timing is retarded ,,just a thought..
 

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Meat Popsicle
91 CRX Si
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2,942 Posts
Tell me a little about the leak down test. I also have a miss every 20s or so when I idle. I drove a full stock 3 stage vtec engine and it ran from fumes and still had a lot of power.
Cylinder leakage tester uses compressed air. There are two gauges, one the reads a defined pressure from the compressor supply and another which reads the amount of pressure that the cylinder sustains. You subtract the two values to determine the cylinder leakage.

Far more valuable data than a compressor tester and it’ll give you audible clues as to where the leakage is occurring from. You can hear the air hiss from the dipstick tube if it’s the rings or from the cylinder head if it’s bad valve seals.

One of be beat diagnostic tools I’ve bought.

OTC 5609 Cylinder Leakage Tester Kit https://www.amazon.com/dp/B0030EVL60/ref=cm_sw_r_cp_api_i_UYLVCbEAP5W1T
 

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Discussion Starter · #9 ·
Thanks for the info. I shift the dizzy back to where it was when it was tune and I get some low torque now. My mechanic did some tune up and shifted the dizzy.
 
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