StephTell

Evening all,

I'm working on a very simple turbo set-up on a bike for someone and I'm wondering what you would consider max boost for stock engine (apart from fuelsystem: that has bigger capacity pump, bigger injectors and rising rate fpr)?

The comp.ratio is 9.5:1

Opinions please

Cossie Sean

ive delt with 11:1 and 40+psi on YB`s so its all down to cam timing, mapping (managment!) and engine internals!!

StephTell

I know what you mean but as a safe maximum in general: does 7 psi sound like much or...?

Cossie Sean

no but im not familiar with the cam timing, ignition map or piston dimensions/materials

jamie's

as cossie sean has said, theres so much more to it than the comp ratio(that is part of it)
the ign map and octane rating of the fuel, the design of the piston crown, the piston/rod strength/structure, cam timing/duration etc
its all quite complicated, if its on mapable management then just up the boost a little at a time while mapping
7psi doesnt sound like a huge amount but i've see engines with det at less and engines running high comp running way m,ore boost so impossible to say

turnover

Stock engine probably 12 psi ,unless it runs forged pistons as standard

StephTell

Lol enginemanagement is not mapable, it's a basic old EFI-system with 4 tb's, larger injectors and a rising rate fpr with upped pressure.

Rough, cheap and simple

Crank and rods will easily handle the strain but I'm more worried about the pistons or headgasket letting go...

The stock engine has 120 bhp, guy only wants around 150 or so...reckon 7 psi should do the trick...

J1mbo

iTrader: (1)

At 3000rpm and sparking after tdc on race fuel by any chance?

As said there are so many variables.

I would say 7psi would be safe as long as you check the fuelling carefully. I follow the Honda scene a little and the standard 11:1 cr k20 they supercharge to 300 at 8 psi and turbo to a little more from 8-11psi but they are fully mappable.

Rs1

iTrader: (1)

Impossible to answer.
Get some det cans and a egt monitoring and start cranking it up until you see bad things happening then back off a touch,lol.

stevieturbo

There is no simple answer.

And fueling is the easy bit, as it isnt difficult to make that safe even if it isnt optimal. Timing for the most part is the critical factor. So what control do you have over this ?

And timing you can make use of will depend on fuel, air temps etc etc. Detonation will be the killer of the engine long before boost or power itself.

StephTell

Timing-wise I could fit a simple programmable ignitionkit like the Dyna 2000 with several advance/retard curves?

stevieturbo

It looks like it would be a crude option. But it would be feasible if that's all that is readily available.

I'm not in bike circles, so dont know what people would use or do, or what fits easily.

Hard to know at which point it's best just to install management that can be fully tuned properly though....which of course is the best option.

Cossie Sean

Jimbo,

it was a 34mm IHI turbo/restricter`d WRC ***FMC Escos, on the P8 (Gems internal`d ECU)

the map was, "interesting" but Lindsay Shaw had a lot to do with that particular build, the cams and headwork were insane, HUGE lift....... so much that the head castings were tweeked so the cam lobes didnt foul!!


with regards to bike engines,

Harmonic ressonance is the biggest killer,
i.e "rod knock".....
they have very very shallow pistons for light weight and long rods for the high revs they produce,

think about pre-ignition, poor mapping at mid to high revs (again dependint purely on cam timing, fueling and ignition, think about this before buying anything mate)

Sean