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Hacking up Honda's ECU
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PostPosted: Mon May 25, 2009 8:57 am 
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Location: Sun City, Lithuania
Hello,
I have a european '91 CRX with a D16Z5 engine and i wonder what maximum compression ratio can I use on EU standard 95 Octane gas. I don't want to use 98 Octane because it is too expensive for a daily driver and not every filling station sells that (it might be a problem with a 35 liter tank :)).

Some info:
My engine is stock except for custom intake and free-flow exhaust and chipped ECU (PM7).
The D16Z5 is rated at 124HP and is basically a D16A9 (130HP) + Lambda and Cat. (cutting the Cat. brings those 6HP back). Those engines are the same as a four bolt blacktop cover DOHC ZC.
The stock comp. ratio is 9.5:1.

I found that it is safe to run at 10:1 CR but has anyone tried going above 10 with 95 RON?


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PostPosted: Sat May 30, 2009 8:24 pm 
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Location: Northeastern New York
I am sure if properly tuned you can run much higher compression than 10:1. I run 13:1 compression in my Crome tuned B18C1 on 93 octane and have no issues.


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PostPosted: Sun May 31, 2009 8:03 am 
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Location: Dublin
93 octane (US) would be about 97-98 ron, 95 ron is about equivlent to 91 octane in the US. I have tuned a 12.5:1 ITR on 95 ron, but had to pull some timing in spots. I would think you would be fine up to 12:1 or so, 11:1 would probably pretty ideal for a street car.


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PostPosted: Sun May 31, 2009 3:57 pm 
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Location: Sun City, Lithuania
A local mechanic told me the other day that high compression yealds higher temperatures which can literally melt the pistons. He told about a Ford Mondeo he tuned a couple of years ago. After 10,000 km on about 13-14 comp. ratio the pistons were scrap. I'm really confused about all these risks.. How much of improvement in power and maybe economy should I expect at 10-11 comp. ratio?

It seems you are Confusing RON (research octane number) and AKI (anti-knock index). RON is used in Europe and generally is about 4 numbers higher than equivalent American AKI.
Wikipedia explains everything best:

Research Octane Number (RON)
The most common type of octane rating worldwide is the Research Octane Number (RON). RON is determined by running the fuel in a test engine with a variable compression ratio under controlled conditions, and comparing the results with those for mixtures of iso-octane and n-heptane.


[edit] Motor Octane Number (MON)
There is another type of octane rating, called Motor Octane Number (MON) or the aviation lean octane rating, which is a better measure of how the fuel behaves when under load. MON testing uses a similar test engine to that used in RON testing, but with a preheated fuel mixture, a higher engine speed, and variable ignition timing to further stress the fuel's knock resistance. Depending on the composition of the fuel, the MON of a modern gasoline will be about 8 to 10 points lower than the RON. Normally fuel specifications require both a minimum RON and a minimum MON.


[edit] Anti-Knock Index (AKI)
In most countries (including all of Europe and Australia) the "headline" octane rating, shown on the pump, is the RON, but in the United States, Canada and some other countries the headline number is the average of the RON and the MON, sometimes called the Anti-Knock Index (AKI), Road Octane Number (RdON), Pump Octane Number (PON), or (R+M)/2.


[edit] Difference between RON and AKI
Because of the 8 to 10 point difference noted above, the octane rating shown in the United States is 4 to 5 points lower than the same fuel elsewhere: 87 AKI octane fuel, the "regular" gasoline in the US and Canada, is 91–92 RON in Europe; 93 AKI octane fuel, the "premium" gasoline, is 97-98 RON in Europe.

However most European pumps deliver 95 RON as "EuroSuper" (equivalent to 90–91 AKI). In Germany, Great Britain and some other countries 98 RON as "SuperPlus" (93-94 AKI) is available almost everywhere. Even 100 RON (95-96 AKI), is widely sold; 102 RON at selected stations.[2]


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PostPosted: Mon Jun 01, 2009 5:49 am 
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Location: Dublin
I wouldn't suggest anything over 12.5:1 for a pump gas motor, E85 would work though. 11.5:1 should make decent power for a street car safely. Boost is better tho :lol:


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PostPosted: Mon Jun 01, 2009 3:12 pm 
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Location: Northeastern New York
I agree that the higher in compression you go, the more likely you are to have tuning and driving issues. Mine is a daily driver but as has been previously stated by other's, I removed a lot of timing across the entire map. But then again, my engine combination is VERY efficient and doesn't require that much timing to make really good power and mpg.


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PostPosted: Mon Jun 01, 2009 3:44 pm 
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inspector01 wrote:
I wouldn't suggest anything over 12.5:1 for a pump gas motor, E85 would work though. 11.5:1 should make decent power for a street car safely. Boost is better tho :lol:



I'm going to wait a few years for E85 to come and I'll slap a small responsive turbo to make my rearview mirrors a bit less crowded. It's a pity that new stuff like E85 is so late to come to Lithuania.. :(

I just can't find out what EXACTLY do I need to change to run E85.
As far as I know I need bigger injectors and a more powerful fuel pump. The thing that bothers me is that many people say that fuel rail, lines and tank must be changed because ethanol doesn't tolerate anything other that stainless steel.


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PostPosted: Tue Jun 02, 2009 4:48 am 
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ThunderFX wrote:
inspector01 wrote:
I wouldn't suggest anything over 12.5:1 for a pump gas motor, E85 would work though. 11.5:1 should make decent power for a street car safely. Boost is better tho :lol:



I'm going to wait a few years for E85 to come and I'll slap a small responsive turbo to make my rearview mirrors a bit less crowded. It's a pity that new stuff like E85 is so late to come to Lithuania.. :(

I just can't find out what EXACTLY do I need to change to run E85.
As far as I know I need bigger injectors and a more powerful fuel pump. The thing that bothers me is that many people say that fuel rail, lines and tank must be changed because ethanol doesn't tolerate anything other that stainless steel.



I run E85 in my integra, Walbro 255, 1000cc injectors, and an aftermarket rail (not necessary), everything else stock with no issues. 383 whp so far, going for 400+ this summer.


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PostPosted: Wed Jun 03, 2009 12:16 am 
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Well, let's hope that Honda made the fuel lines resistant to vodka :wink:
I'm looking to have this car for as long as I can so I really don't want to mess up the fuel system.


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PostPosted: Wed Jun 03, 2009 4:16 pm 
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Location: Northeastern New York
Oh yes!! ALL my Russian Comrads LOVE vodka!! Hopefully our Japanese buddies do too! ;-)


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