stever951

Any recommendations on a safe level of boost on a K27/6? Who's suffered head gasket failure on a K27/6 and what boost levels were you running and with which mods?

Steve

Ski

wrong question - what is a safe air/fuel ratio before the mixture goes lean to cause high heat/detonation to cause HG failure? Keep your A/F ratio between 11.9-12.5 on boost.

Yes, excuse my manners, welcome to the board.

Tom M'Guinn

Welcome to (posting on) rennlist Steve!

You can't really get meaningful info by equating blown HG's to certain boost levels. As Ski says, its more about how your car is set up and its tuning (including octane).

How are you controlling fuel now, and which chips and injectors do you have? Even with well-mathced chips, the stock injectors will not supply enough fuel to get the most from that turbo.

ibkevin

That's an afternoons worth of reading by itself. Keep in mind, on an 18yo plant these ??'s have been covered extensively, stroll through the archives and you'll see what I mean.

You couldn't have found a better site with more knowledge on 951, ok PAG--maybe.

Welcome aboard

stever951

Hi guys
My situation is this. My car is currently running it's original K26/8 with an Apexi S-AFC fuel controller and AVC-R boost controller, 3 bar FPR, Lindsey DP WG, cat bypass and Promax MAF. It made 293 whp on Friday at 1.27 bar boost but was running lean at the top end. I'm about to upgrade the injectors so thought I might put on the K27/6 I bought from badcoupe last year while I'm at it. there's been a lot of talk recently about back pressure with regard to the K27/6 and how it might contribute to detonation/head gasket failure and I wondered at what boost level this might happen (during track conditions assuming correct air/fuel ratio).

Steve

Tom M'Guinn

You might want start by checking with Promax about their MAF's flow limits. Does that MAF have the range to work with a big turbo at higher boost levels?

eclou

Mine blew the HG after 2-3 road race weekends and a lean midrange at 18# boost. A well tuned 26/8 is almost as powerful as a 27/6 at sane boost levels. I wouldn't bother changing unless you mate yours and produce a 27/8.

RK951

Can the Promax Scivision MAF be used with a larger turbo? I haven't heard of any way to tune it like tweak it with piggyback unit like other MAFs so I don't see how it would be a good match for a larger tubo. Perhaps Andrew or Thomas could comment. Maybe you should ask in the Promax MAF thread as I'm sure there are others interested in hearing if the Scivision MAF can be used with turbos other than the K26.

stever951

The Promax MAF can be used with larger turbos. Somebody at the dyno day at the weekend made over 400 whp with a Promax MAF and Lindsey turbo amongst many other things. I think the charts should be on www.cannell.co.uk in the next few days.

RK951

How can you do any tuning with a Scivision MAF? Is there a piggyback unit that it will work with?

hally

A simple piggyback like the pro-m power perfect is ideal for dialing in a MAF - you transparently modify the Vin -> Vout relationship.

Don't bother with a trick 3D, RPM based etc etc unit unless you need the extra features for water injection, logging etc.

RK951

So would a Lindsey Mafterburner work with Scivision MAF?

stever951

Dyno day results from the weekend now up at http://www.cannell3.co.uk/944%20UK%20League.htm

caster951

Sent you a PM about the Apexi. Any help would be appreciated.

Chris White

Just to add a little more technical answer –
Your head gaskets life is dependent on many things, the thing that will end its life is detonation/preignition – not boost levels.

There are two prime causes of detonation/preignition. Lean mixtures and high intake charge temps.

Lean mixtures are caused my incorrect management tuning - easy enough to fix. High intake temps are created when a turbo is operated outside of its efficiency range – a little more expensive to fix (different turbo).

The rest of the engine just determines how long you can run with detonation (head gasket, Orings, general state of health) with out a failure.

Chris White