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Old 28-01-2006, 04:31 AM
Revhead Revhead is offline
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Default Suggestions on engine setup and water/methanol mixtures.

Hello all,

Being a newbie here, I would really appreciate it if you could advise me on the setup I intend to run.

Im about to purchase a mini car for daily driving with 4 cylinder 1300cc Naturally aspirated with variable valve timing.. Static compression ratio is 10:1, power is quoted at 85hp and redline is around 7200rpm.

Havin tested the demo car, I feel that a light pressure turbocharging may be necessary to increase power. My goal is an additional 20-30hp.

The thing now is Im a little concern about fuel mixtures not sufficient for the additional air pumped into the engine by the turbo(intend to run 8-10psi with an air-air I/C).

I understand that water injection(say 50/50 W/M mixtures), would allow leaner fuel mixtures and additional ignition advance. Am I correct?

Say if I run water injection, do you guys reckon that I could get away without any changes to the ECU's factory mapping for both the ignition and fuel timing with a 50/50 W/M injection?

Or should I run more methanol(40%W/60%M) to counter the lack of my fuel supply as well as the N/A ignition map?
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  #2  
Old 28-01-2006, 10:36 AM
Richard L Richard L is offline
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Welcome to the WI forum.

You propabably need more fuel then your stock injector can supply. Running 8-10psi will get you more than 20-30bhp. Additional fuel can be supplied by additional injector driven by a piggyback ECU.

WIA can be use to keeping things cold and suppress the onset of knock. But I doubt if you can get away with adding alcohol to suppliment extra fuel requirement for 8-10psi.

50/50 will help you running 8-10psi. Your effective compression ratio will be around 12:1
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Old 28-01-2006, 10:53 AM
JohnA JohnA is offline
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Default Re: Suggestions on engine setup and water/methanol mixtures.

Quote:
Originally Posted by Revhead
....I understand that water injection(say 50/50 W/M mixtures), would allow leaner fuel mixtures and additional ignition advance. Am I correct? ?
you are correct in the following sense:
Without W.I. you'd probably need 50% more fuel under full boost and 10degrees of retarded timing (example!)
With water/meth injection you may get away with 30% more fuel and 5 degrees of timing

More power needs more oxygen (provided by the turbo) and more fuel (provided by the fuelling system)
So 30% more power at the wheels will need 30% more oxygen molecules and 30% more fuel --- not much leeway there

You will not be needing the *extra* fuelling that is typically used for in-cylinder cooling under boost --- that is over and above the fuelling needed to support your extra power. The WI will cater for this missing 'extra' fuel.

(I am just elaborating a bit on Richard's take) :smile:
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  #4  
Old 28-01-2006, 01:10 PM
Revhead Revhead is offline
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Many many thanks to you Richard and JohnA.

I won't run additional injector(s) (assuming you recommend me fitting it pre TB), cause Im a bit paranoid with back-firing when the throttle is shut. I do wonder what is the effect of actually fitting the additional injector(s) along side the water injection pre TB?

Apart from that, I can't run additional injectors post TB as the factory intake manifold is made out of plastic. I doubt superglue could hold up so unless I fabricate an aluminium intake manifold and runners(where power gets to serious levels), then I'll go for this. Furthermore, things get complex with the extra injectors on each runners(extra fuel rail, fuel lines) as there's more things to fail.

There's a big likelyhood that Im gonna run a piggback Greddy E-manage and run bigger primary injectors, cause I don't want the hassle of tuning the cold start, injector priming etc like what you do in a stand alone ECU. I may have to make a return fuel line and fit a FPR.

Back to the topic, Im gonna go a bit radical here so let's say..I want to run more boost, I fill in my tank with straight Avgas and 40%W/60%M injection, I do reckon it is possible(but not necessarily safe, due to engine's components strength limitation..etc) to run up to 12 psi due to the slower burning mixtures right?

Now, I'd like to hear most of you forummers here's experience of getting away with pinging and lean mixtures with water injection (assuming its 50%W/50%M mixture).

Besides hearing knock ,how do guys know you're at the outer limits of the water injection system? What sort of A/F ratio and EGT we're looking at?

I found this article from SDS efi,

http://www.sdsefi.com/techegt.htm

Here's a few words which kinda confuses me,

Quote:
It should be mentioned that the target EGT is valid only on the same engine configuration as was used on the dyno. If you change the ignition timing, cams, pistons, headers etc., the optimum EGT may also change. Raising the compression ratio with no other changes will drop the EGT at the same AFR. Retarding the ignition timing will generally raise the EGT at the same AFR. One engine might make best power at 1350 degrees while a very similar engine might be happier at 1500. You can't guess at this or you are simply wasting your money on the instrumentation. Wankel engines have higher EGTs than comparable piston engines due to their lower thermal efficiencies. 1800F is not uncommon here.

Some gauge manufacturers say you should tune to achieve maximum or peak EGT for maximum performance. This is incorrect. Peak EGT generally occurs at an AFR of around 14.7- 15.0 to 1 on gasoline. This is far too lean for maximum power and is dangerous under continuous WOT conditions. Many people think that the leaner you go, the higher the EGT gets. This is also incorrect. Peak EGT occurs at stoichiometry- about 15 to 1 for our purposes. If you go richer than 15 to 1, EGT will drop and if you go leaner than 15 to 1 EGT will ALSO drop. It is VERY important to know which side of peak EGT you are on before making adjustments. It is safe to say that peak power will occur at an EGT somewhat colder than peak EGT.

Any words on this?


Again, many thanks for the reply. Really appreciate it.
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  #5  
Old 28-01-2006, 02:30 PM
Revhead Revhead is offline
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I forgot to mentioned that,

Is it correct to say that since turbocharged engines have higher B.S.F.C(i.e 0.55-0.60),due to fuel dumping to cool down combustion temperatures, and that running water injection can lower it to the level where naturally aspirated engines are running(0.45-0.55) by using a leaner/weaker mixture?
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