Turbobike Web Site www.Turborick.com

Re: [turbobike] Re: SOHC Honda headgasket problem

John C Williamson (john.williamson5@virgin.net)
Fri, 21 May 1999 13:46:14 +0100

Hi again!

I doubt that stock advance will be OK, because if you double the gas charge
in the cylinder, you double the effective compression ratio! This makes the
charge burn twice a fast, so theoretically you need half the advance that
you did. Half the advance does not mean half the degrees, but half the mm
before top dead centre, or even less advance if you want to be safe.

On the other hand it is doubtful that you actually are getting detonation if
you are using 50/50 methanol petrol mixed. You probably just have too much
advance causing very high cylinder pressures, before tdc, and at tdc, which
does not help power output at all.

Anyway what do I know! These things are never that simple.....

----- Original Message -----
From: Joe Allan <beak@seaside.net>
To: John C Williamson <john.williamson5@virgin.net>; Bob Shammas
<b.shammas@worldnet.att.net>; Rick <gsxr1100@ptw.com>; Turbo list
Sent: 20 May 1999 23:56
Subject: Re: [turbobike] Re: SOHC Honda headgasket problem

> John and fellow listers;
>  Good info John, thanks, I didn't mention it in my original posting but I
> running a 50/50 mix of gas/ alcohol in the supercharged SOHC, I would run
> 100% alcohol but the internal passages in the carb are too small to
> accommodate that much flow (suck through system, bigger carb coming), my
> thinking is that the alcohol will help the detonation problem. I run the
> timing at the stock advance setting...is this ok?...thoughts, help
> gratefully accepted.
>  Joe Allan
> -----Original Message-----
> From: John C Williamson <john.williamson5@virgin.net>
> To: Bob Shammas <b.shammas@worldnet.att.net>; Rick <gsxr1100@ptw.com>;
> list <turbobike@natvideo.com>
> Date: Thursday, May 20, 1999 3:45 PM
> Subject: Re: [turbobike] Re: SOHC Honda headgasket problem
> >After thinking about this for a bit I think that the main reason that
> >gaskets 'go' as such (apart from the oil seep / cappiliary problem) is
> >the head may 'lift'. The PEAK cylinder pressure goes up enormously with
> >ignition advance but power output may only increase marginally. So if you
> >have clamping / barrel stud strength problems causing you to blow gaskets
> it
> >makes much sense to reduce full advance to a lower figure, and up boost
> >instead, producing less peak pressure but more where it counts ie, later!
> >when the crank is in a better or more advantagous position to take
> advantage
> >of the increased cylinder pressure to produce more torque from less
> >pressure. I suspect most detonation / pre-ignition / head gasket probs
> >caused by too much advance.
> >This is one of the reasons that Nitrous does not seem to cause detonation
> >and head gasket probs as often, because it is inert (and can put out
> fires!,
> >like C02 does!) and only breaks down into Oxygen & Nitrogen (most of the
> >atmosphere - and does not support combustion) LATER in the chamber as it
> >takes time for this to occur. Just the same as less advance really.
> >
> >So basically if you want to go fast safely, go rich - less advance - and
> >loadsa boost and Nitrous and you will not break the engine.. look for
> >smoke (a little!) and anything that sounds harsh or 'pings' (you cannot
> hear
> >it on a bike...) nedds less advance... This will still blow gearboxes /
> >clutches etc,  even more so in fact but the motor should be OK without
> >expensive parts.
> >
> >I welcome your coments (Rick?) , anybody!
> >