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Fuel enrichment

What is the simplest and maybe most economical way of fuel enrichment for an increase in engine safety for a mild boost increase. I want to run to 1.0 bar and currently a a k-27 turbo, b & b headers.

I need ideas and the steps to which this is accomplished for a solution.

I do not know if Andial sells the fuel enrichment package any more.

Thanks greatly,

Jerry S
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Old 08-20-2010, 09:44 PM
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You may not need it. Your AFR's should be checked before you add boost so you know where you stand. If not marginal then add boost and re-measure AFRs. The best way to add fuel is through an adjustable WUR, either manual or digital. That is the only way to tune the fuel curve.
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RarlyL8 Motorsports / M&K Exhaust - 911/930 Exhaust Systems, Turbos, TiAL, CIS Mods/Rebuilds
'78 911SC Widebody, 930 engine, 915 Tranny, K27, SC Cams, RL8 Headers & GT3 Muffler. 350whp @ 0.75bar
Brian B. (256)536-9977 Service@MKExhaust Brian@RarlyL8
Old 08-20-2010, 10:20 PM
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Sounds great, to check the AFR's is a O2 sensor with onboard guage the best way and if so, what is the minimum ratio that would be considered a safe region.

Also with an adjustable WUR, how is this accomplished ? I have seen an electrocnic one on pelican for an SC but not a turbo. I read of a procedure to convert your existing WUR to an adjustable unit.

Jerry S
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Old 08-21-2010, 11:33 AM
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Crotchety Old Bastard
 
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It is generally accepted to target boost AFR at 11.8 +/- 0.2 :1
An adjustable WUR can allow you to manually adjust the boost control pressure as well as cold, warm and threshold. Typically the DIY adjustable WUR will only address the cold pressure as it is most problematic on old units.
Again, you may not need this at all and won't know until the AFR's are measured. That is best done with an LM-1 or on a dyno. A data logger is required as you do not want to be looking at anything but the road when on boost.
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RarlyL8 Motorsports / M&K Exhaust - 911/930 Exhaust Systems, Turbos, TiAL, CIS Mods/Rebuilds
'78 911SC Widebody, 930 engine, 915 Tranny, K27, SC Cams, RL8 Headers & GT3 Muffler. 350whp @ 0.75bar
Brian B. (256)536-9977 Service@MKExhaust Brian@RarlyL8
Old 08-21-2010, 01:47 PM
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Agree with the above.

I would not run a true 1 bar without an intercooler upgrade.

Which K27?

For some the first simple effort at more fuel is usually resetting base CO up to 3.5%. This can also help throttle response off idle.

Second simple effort might be to shim the fuel pressure reg on the Fuel Distributor to raise System Pressure.

Both these can be done with a wide band or on a dyno.

Next is some way to lower Control Pressure as controlled by the WUR. (Andial Fueler dose this.)

The Andial has for the most part been replaced with the Adjustable WUR along with an boost-clamp (rpm switch and solenoid) that delays enrichment for the most part. Almost dose the same thing except a little better in that it dose not have as much potential for the to rich mid rpm section that came with the Andial.

After that it gets more involved and going to a Fuel Distributor that is modified for more fuel from: CISFLOWTECH However, this takes some effort to master.

Another possibility is active boost control by RPM that can taper boost when the fueling system ceiling is reached. This has the potental for a bigger mid range power.

Condition of the CIS (ballance), the efficency of your turbo, intercooler and ignition settings in part determins what you can get away with on AFR's. In my non expert opinion at TQ peak you probably do not want to be any leaner than 11.5. At HP peak should probably not be over 12/1. At red line on boosted 930's many will find they are running close to 13/1. This is often livable on a street car though probably less than desirable.

There are a lot of good threads on this here if you want to look further into it.

Last edited by 911st; 08-21-2010 at 06:13 PM..
Old 08-21-2010, 06:09 PM
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I am running a K-27 (I believe an 1100), and I have a Garretson intercooler. My timing is setup quite conservative.

It seems odd that going to 1 bar on these cars is questionable however the factory has been running these boost levels plus a higher static compression ratio on their newer cars like the GT2's, etc. (Naturally, there are other systems at work in the new cars like knock control, electronic fuel and ignition, etc).

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Old 08-22-2010, 02:28 PM
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1.0bar is common and safe when used with a larger intercooler, which you have.
I think the confusion comes from reading the efficiency island graph of the K27-7200. The 7200 becomes less efficient past maybe 0.9bar. Does that mean you can't run 1.0bar? No, only that a K27HF will do it better.
Does your K27 have the numbers "7200" and "11.11" on the tag?
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'78 911SC Widebody, 930 engine, 915 Tranny, K27, SC Cams, RL8 Headers & GT3 Muffler. 350whp @ 0.75bar
Brian B. (256)536-9977 Service@MKExhaust Brian@RarlyL8
Old 08-22-2010, 03:12 PM
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Quote:
Originally Posted by 911st View Post
I would not run a true 1 bar without an intercooler upgrade
I wouldn't run 1 bar without a turbo upgrade if the turbo in question is a K27-7200.
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Old 08-22-2010, 03:43 PM
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Paul,

I do not believe the problem with the K27-7200 is it going out of the compressor efficiency range at 1 bar or going postal and overly heating the charge air.

Before that happens the turbine hot side chokes and limits the compressor sides potential.

The key to running a 7200 seems to be on the hot side and making the exhaust work as well as possible.

Note how well it responds to Brian's equal length headers and an open muffler. My point of reference is on my car I switch from a B&B muffler to a straight through Borla muffler I built and picked up 30hp on the dyno. It just dose not seem to make sense that headers or a muffler change could make that much differance.

In further support of my thought on this, the 7200's compressor is probably more modern and more capable than the K27-7006. However the 7006 makes more HP. This seems to be due to its larger flow hot side which dose not choke as soon and also makes for less exhaust reversion at the same boost levels.

As another point of reference, on my car, which was kind of out there for CIS (cams, ports, euro injectors and lines, larger bar and plate re-core of my C2 intercooler, custom programmable WUR/fueler, headers...), all a 1 bar spring did was fill in my mid range some. Even with a EBC and Tial trying there best to pull 1 bar I could not maintain even .9 bar at HP peak on a load dyno.

In the end I preferred the K27-7200's kick over my K29 and HF prototype which both had a bigger top end. Not that it was better, it just suited my in town and back road driving style better. As a side benifit, at full boost and with control pressure lowered as far as possable I was able to maintain 12.2/1 AFR to 6700rpm. With the K29 an addational injector was needed to keep the AFR's in line (not suggested).

In fact I kind of suspect the larger turbos that can achieve and hold more boost at higher rpm might even make for more of a need for improved intercooler capacity than the 7200 now that I think of it.

I guess I do not believe running a 7200 at 1 bar puts a CIS turbo and any more risk than a larger turbo at 1 bar. It is actually probably safer if anything as it limits boost to keep the motor withing the fuelling limits of the stock CIS system.

Thus, I whole still would not run 1 bar without an intercooler upgrade and I have no issue with running a K27-7200 at 1 bar.

But, that is just my opinion.

Last edited by 911st; 08-22-2010 at 08:30 PM..
Old 08-22-2010, 07:27 PM
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