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Discussion Starter · #1 ·
85 hp GX vs. 102 hp RD
Why does one motor have more HP than the other? One came in the golf/jetta, the other in the GTi/GLi. Both have 1.8L. Same bore, same stroke. Both used CIS-e. Both are 9:1 compression ratio. Why does one motor have 17 HP more than the other? I have both motors. I have both in 1979 Rabbits. Same exhaust, same CIS injection. I dont feel a lot of difference.
 

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Re: 85 hp GX vs. 102 hp RD (blacked out gti)

GX are 9:1 compression ratio... RD are around 10:1...
GX had smaller valve head, RD has larger valves...
GX used CIS-lambda, RD used CIS-E...
GX used Tci-h old style electronic ign., RD used knock box ignition...
GX can make alot more power - just swap a JH head onto it and boost it

regards,
Peter T.
 

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Re: 85 hp GX vs. 102 hp RD (The_Hamster)

Are you guys sure about the compression ratio? I found a web site that says both are 9:1. Is one a solid lifter, and the other a hydrolic lifter? What are the vlave sizes for each engine?
 

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Re: 85 hp GX vs. 102 hp RD (blacked out gti)

all A2 motors except the early diesels are hydraulic lifter.
that is all 85+ golf and jetta's, except the 85-87 diesels.
yes gx is 8.5:1, MZ is 9:1, and RD is closer to 10:1, but not quite i believe.
 

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Re: 85 hp GX vs. 102 hp RD (The_Hamster)

Quote, originally posted by The_Hamster »
both did not have single outlet, the RD had dual downpipe IIRC.

I have 2 RD engines, both from '86 GTI. Both had single outlet manifolds with a donut coupling to a single downpipe from the factory.
 
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