Speedtoys

Raybeatis St41 yo front, st43 in rear.

Bill Ball

10:5 is way too fat. Why do you want to raise fuel pressure? You're fat all over, especially for an NA motor. In theory you should drop fuel pressure (although not too much if you want the injectors to work well) or install smaller injectors, unless we can Sharktune.

Speedtoys

Mark, shark tune or put a carb on it.




You probably understand carbs better.

IcemanG17

YUP..........these are the brakes on Seans 52 racer......WOW....much better than my st43-43 setup.....they also last a LONG time

IcemanG17

MK
10.5 from 5500 UP.......................that is silly....I'm amazed it even runs at all...... You REALLY SERIOUSLY need sharktuning.....we don't even need a dyno to do it.....install a wideband (you can borrow mine) and get jeff to ride with you......my wideband (PLX) data logs......super easy....

For example....on my tiny 4.5L engine...when I got it the timing was set at 30' flat from 3000 up.....fuel was FAT at 11.4...I leaned it down to around 12 and got 243-257..... I increased timing to 31 from 3000-5250 and 34' from 5500 up...now I have 265-289 massive gains....my AFR still is quite rich...the dyno (tailpipe) showed 13 in midrange and 12.4 up top...my header WB02 shows about 12.8 midrange and 11.8-12.0 at 6k....so I have more to gain as well.... my plugs read near perfect, possibly low on timing-temperature.... I think can either increase timing up high OR lean it out.....

However the S4 engine, especially a stroker like yours is VERY different...high compression engines require LESS timing...keep in mind mine is only rated at 9-1 with cranking pressures (factoring cam timing) of maybe 155psi...so quite low....even the BMEP for my engine is quite modest...184psi at torque peak and 159psi at HP peak....

Enough playing around with BS tunes......its time to invest in a proper tune for your engine..... my guess.....400whp EASY.....

mark kibort

I was thinking to get a lesser flow injector and then the pressure could be raised. 40psi is a little low. (thinking about better atomization at higher pressure) you might have missed the point of me wanting to change out the 30lb injectors for the 24lb type.

sure, its drowning from 5500rpm and up, but whats the HP loss from going that rich? ive heard there is much more gains from lean to optimal, but rich to optimal, is usually not that dramatic. plugs look good and because i have a very narrow range of a fuel ratio goal, maybe the 24lb injectors can hit the 12.5:1 range without any tuning...... the only think i cant do is the timing part. you said that the higher compression engines like mine at 11:1, dont need the advancement? if so, then maybe that cant be changed safely. or maybe retard for HP at the top rpm.
anyway, sure, i think 400rwhp sould be atainable, but just dont know where it will come from. anderson and fan both had the bigger valves and cams when they were making the 410 to 420rwhp. they didnt have any tuning either.

mark kibort

ha ha !

as you might remember, i cant really do a shark tune. I dont have the ECU that is stock and has the right connections. however, we did take it for a ride .(with bill) and we could see where i was at mixture wise. its just bad 5500 to 6500. should be pretty easy to tune out that fatness. i could go a little lower on pressure with the fuel regs, but below 43psi, might not be the best. i would rather go to the 24lb injectors and maybe put the pressure back to stock 50psi ish. Remember, with 19lbers , i got to 12.5:1 and used 70psi to do it and got 335rwhp out of a 5 liter. Sure, the sharktune is the way, but in this narrow range, its pretty easy to get the ratios in the right range of about 12.5:1, without other areas being too far off. the part throtttle stuff is handled well by the closed loop system (cept for idle if it is way rich) and i dont need any WOT performance at anything lower than 4500rpm. I dont think im too far off there, as its still 400rwt at 4500, and i think the most anderson got was 420 back then! I dont know what kind of timing we need at the top end to optimize HP, but if we need to advance, that might be hard with my current ECU system

I do have a GT computer handy.... heck,, maybe plug that think in and see what happens.

mark kibort

For example....on my tiny 4.5L engine...when I got it the timing was set at 30' flat from 3000 up.....fuel was FAT at 11.4...I leaned it down to around 12 and got 243-257..... I increased timing to 31 from 3000-5250 and 34' from 5500 up...now I have 265-289 massive gains....my AFR still is quite rich...the dyno (tailpipe) showed 13 in midrange and 12.4 up top...my header WB02 shows about 12.8 midrange and 11.8-12.0 at 6k....so I have more to gain as well...QUOTE]

hard to imagine that you can get 4 degrees of timing advance and get
30hp gain. doesnt make a lot of sense.
(you said you went from 30 degrees to 34 degrees up top)

mark kibort

certainly just the displacement gain from 5 liter to 6.4 liter of 28% should gain close to the same power, which would be 420rwhp vs the 335 i once had. (even at a low of 320 would yeild 410)
sure its not a direct conversion, but should be in that range.

im really temped to get the 24lbers and give it a try.

mk

Speedtoys

The thing is Mark..you are using a 928 ECU, right?

It has certain assumptions on pressure and flow, that when you dork with fuel pressure, you screw it all up.

Basically, you can "tune" your low end, or high end, but because assumptions in how the universe works in the ECU are no longer true, you wont ever get what you need, done.

Catch us up..what LH is in this car?

mark kibort

Here is the dyno run.

the ECU LH box is funky. custom chip (bill knows). the EZK is bone stock S4. I think the GT computer I have access to is just the EZK .
So, im thinking, if I can just tune the high end, I will be in good shape. but I wonder what the gains would be from going from 10:1 to 12.5:1 ? maybe 10 to 20hp?? might be worth a try. or I dump the holbert ECU and go with the stock S4 set up.

Speedtoys

So..whats stopping you from putting a proper LH in it?

Same plugs, same sensors..just..what you have now was a good idea 20yrs ago?

Sharktuner is light years ahead of what youve got.

Bill Ball

Mark:

Yes, a smaller rate injector and higher pressure would be a good idea. Although 40 PSI is still good, dropping pressure further to lean out the mixture is not good, so you're right. The gains from getting it to 12 or 12.5 may not be huge but it would still be worth the effort.

I remember doing some freeway blasts and looking at mixtures, which seemed good, so I guess we got some aspect of the Sharktuner running. I recall your harness was goofy, so we never got it fully working, but my memory is not clear on just what we did. W/o Sharktuning, all you've got is fuel pressure and injectors to play with.

mark kibort

I forget too. I think we had a harness problem. i remember there was a lot of wires where we didnt know wherre they went, but you figured out the basic needs for some looksy! maybe i can try dropping the pressure from 42psi to 40psi and see what that does.


It might be time!

mark kibort

I was talking to Brian who said his car runs 280ish rwhp with a pretty decent fuel air mixture of near 12:1, and only has 37psi fuel pressure.

I do remember tuning my buddies S4 6 liter who had near 15psi and ran ok, but was still running kind of fat for reasons we still don't quite understand.

anyway, Im at 43psi and can easily drop my pressure down to 37psi. maybe that might clear up some richness at the top end. if I can get the mixture in the 12s from 5500 to 6500rpm, where else can I gain Hp by tuning, even with a shark tuner? timing??

I might have to check out running another brain so I can do a shark tunen and see what the potential is of the 6.4 liter with the stock stuff on top of it.