safe psi on premium unleaded

[skinedknuckles]

hi all ,new to posting, but not reading on site ,got a gsxr 1100 bored to 1216 busa pistons & rods gas flowed head by roger upperton 2mm spacer plate, no base gaskets ,cams dialled in ,34mm slaby carbs ,garrett gt2560r roller bearing turbo ,38mm tail external wastegate ,ignition set at 36 deg's  been running on road for year now at 8psi ,question is how high psi can I go on premium pump piss and how high safely on race fuel? thanks skinedknuckles. post pic's later.

[arttu]

Hi,
I don't think anyone can tell how much boost your engine can take as this depends on numerous factors like compression ratio, combustion chamber shape, ignition timing, AFR and so on. But you can always make some educated guess based on few basic factors and assuming the rest are close to the optimal. But just keep in mind that any small thing can ruin the result. For example if you are running lean at some rpm or too much ignition timing it will knock at relatively low boost no matter how good is the rest of the setup.

For any guess it would be important to know the compression ratio. Have you measured it? And are you using any charge cooling like intercooler or water injection?

For reference I have about 9.1:1 compression ratio on my air cooled GSX engine. Normally I'm using water injection to prevent detonation and cool down the intake air a bit but I have done some tests also without water. On those tests I have run it at 15-16 psi with pump fuel (European 98 oct.) and haven't noticed any signs of knocking.  

[katana]

And running without base gaskets on a Gixer is asking for oil leaks like you wouldn't imagine!

[skinedknuckles]

hi Arttu  thanks for reply my compression is in low 9s cant remember exact figure was 18 mth's ago when I built engine, can't find my scribblings/ notes. Had bike on dyno to double check my own afr gauge which is still on bike, its a innotive cheapish and does the job well, ended up putting 132.5 mains in carbs,all new jets  and needles and emulsion tubes no petrol peeing out at 4psi from regulator.Do you think it  would be beneficial to retard ignition a bit more?if so how much? putting out just shy of 200bhp at the mo.No inter cooler but got a head cooler to try and keep temps down a tad every little helps.

hi katana   still no oil leaks in 3000 miles yet. might just be lucky??? just put gaskisinch I think that's what it's called on both sides of spacer plate, it gets thrashed, mucho laughs in helmet, big grin when I get off bike, should be able to get it on prescription.

[greybush]

I run 13.5 psi everyday on 91 pump gas with water/alcohol injection all summer in my 1216 bandit with busa piston approx at 8:1 compression, i retard the  timing 5deg  and have run 15psi with this set-up with no problem. this is what i do and it works for me. In warmer weather i blend in E85 to correct my a/f ratio, my motor really like E85, pull harder when blended.  this set up at 12psi has gone 9.92sec at 149.6mph on pump gas. my a/f never goes past 12.0
i hope this helps.

[arttu]

Oct 1, 2014 20:26:27 GMT skinedknuckles said:

hi Arttu  thanks for reply my compression is in low 9s cant remember exact figure was 18 mth's ago when I built engine, can't find my scribblings/ notes. Had bike on dyno to double check my own afr gauge which is still on bike, its a innotive cheapish and does the job well, ended up putting 132.5 mains in carbs,all new jets  and needles and emulsion tubes no petrol peeing out at 4psi from regulator.Do you think it  would be beneficial to retard ignition a bit more?if so how much? putting out just shy of 200bhp at the mo.No inter cooler but got a head cooler to try and keep temps down a tad every little helps.

With 9:1 compression you should be able to run about 15psi boost IF the combustion chamber shape is decent and AFR and ignition timing are correct. 36° ignition timing sounds a bit aggressive to me but every engine is different in this sense. I probably would retard it by few degrees before turning up the boost. Dyno testing is pretty much only proper way to find correct timing. Start with low advance and increase it until you hear knocking or power doesn't increase anymore. Just remember to watch AFR closely when you turn up the boost.

Better engine cooling helps too but it's slightly different thing than charge air cooling. Usually limiting factor for boost is knocking and that occurs when pressure and temperature of the air charge in the cylinder rise too high. When you turn up the boost the intake air temperature and pressure (naturally) go up too. Charge cooling negates the temperature rise so you can use more boost without knock. 

[katana]

Oooh you fibber - no base gasket my arse - a soft ali spacer AND Gaskacinch is purfect! What I thought you meant was plain barrels to cases ! ! !

[skinedknuckles]

hi all  how do you go about fitting water/alcohol injection  for carbs how much space is need? cost  roughly? how long does it last? dependant on tank size I suppose.1ltr tank be large enough? I have no room for intercooler at the moment may have a juggle about see if I can put one some where.

[arttu]

There are plenty of kits on the market that are suitable with carbs, almost any basic kit will do. One problem with almost all of them is that they use pretty large pump so fitting it on a bike might be challenging. The prices seem to start from about 200€.

Water consumption depends heavily on flow rate, injection triggering boost level and especially riding style. I have a 1.5l tank and on normal street riding it lasts quite long time, at least for 500km. On race track few 20 minute sessions were enough to suck it dry.

Some web links for the kits:
www.coolingmist.com
www.aemelectronics.com/products/water-methanol-injection-systems/water-methanol-injection-kit-for-forced-induction-gasoline-engines
www.alcohol-injection.com/en/19-universal
www.snowperformance.net/index.php
www.alcoholinjectionsystems.com

[skinedknuckles]

thanks Arttu do you know the best place for putting the injecter/injectors? would you fit them like Nos, ie one each cylinder  or just one in plenium.by the way my bike is running a blowthrough system, I can make water bottle fit behind side panel & pump behind rear shocker. Thanks

[skinedknuckles]

    a few pic's of bike I hope, crap on computers

[skinedknuckles]

oops get nephew up to post pics.

[katana]

Water injection NEEDS to be as far from the inlet valve as possible to give maximum cooling effect to the charge - cooling the combustion chamber achieves nothing in comparison.

[skinedknuckles]

 thanks katana so where would the best position for the nozzle be and how do you work out the nozzle size to use? will be putting back on dyno thanks.

[arttu]

It's some kind trade-off with nozzle placement. I think the best options are one nozzle just after the turbo or individual nozzles for each cylinder. Like Katana said having the nozzle far away from the engine gives more time for water to mix with air which results more efficient cooling. Downside is that water may get distributed unevenly between the cylinders as it doesn't flow exactly the same way as air through piping and plenum. Individual nozzles would provide more even distribution.

I don't know which one is better in the end but I would start with single nozzle as it is much simpler and works well enough in most of the cases. I'm using single nozzle on boost pipe just after the turbo. I can see some variation in EGTs between cylinders when water injection activates so probably water isn't shared completely evenly between the cylinders but I haven't noticed any real problems with that.

Typically water flow should be about 10-20% of fuel flow. So roughly something like 200-300cc/min for typical 200-300hp bike engine. But it's better to test on dyno what works best for your engine, if possible. More water may provide bigger intake air temp drop but less power in the end, for example.