Is there any limit to how big injectors Nistune can handle?

John · Post by **John** » Wed Apr 08, 2009 6:26 pm

Hi!

Im planing to run Bosh 1680cc injectors and E85 and was just wondering if there was any limit to how big injectors Nistune can handle. I read that some on on this forum was running 1260cc and E85 without any problems but that was a while back. Is there some one out there that has succesfully configured Nistune with rely big injectors?

Regards

John

chris2712au · Post by **chris2712au** » Thu Apr 09, 2009 9:38 am

Sory to not be able to advise from experience... but the theory..

Those are massive injectors.. I dont think the idle will be really good but might be ok if it is set high enough.. reason being you would have a significantly small injector pulse width and it would still give enormous amounts of fuel nistune may not be able to deliver such short pulse widths.. and the fuel atomisation could be a problem.. then there is the 'K' constant.. pretty much the ratio from AFM voltage to injector pulse width this will be where I think you will struggle... normally afm and injectors are swapped as a pair... which AFM do you tend to use ? normally for example 550's and z32 are changed together and the K value is pretty much the same.. however if you were to keep a standard AFM and just go larger with the injectors the result would be lower K values hence if you change the AFM and leave the injectors you would need larger K values..

So I beleive your K will have to be extremely small... if the nistune can handle that. It would be best to size injectors and afm at the same time.. so best to change in pairs..

I hope that info is correct however play around with afms and injector combos in the resize function and see for yourself..

4 x 550s can make well 250rwkw thats 2200cc in total to run the whole motor not per cylinder...

datsunboy · Post by **datsunboy** » Thu Apr 09, 2009 3:37 pm

to need 1680cc injectors per cylinder must make this engine one HELL of a monster!

John · Post by **John** » Thu Apr 09, 2009 7:45 pm

chris2712a - Thats my biggest worry that the shortest pulse to the injector will still deliver to much fuel and my idle will be crap.

The thing is that when your running E85 it takes 30 to 40 % more fuel to get the same AFR ratio as you would like to have with gasoline so 1680cc is realy some what like 1000cc or 1200cc injectors.
The lucas Disc injector @ 1260cc is only god for abaout 500 E85 horsepower, What you could do is just up the fuel presure to get more out of them but that just seems to be a temporary solution and thats why i whent with the 1680cc injector.

Im running the standard AFM element in an 3" pipe at the moment but switching the Z32 AFM. Will have to find another solution for when that AFM bottoms out.

I did the K value calculation from the Tuning documention and with the 1680cc injector the K value should be 4.7 something, this was with the standard AFM

Regards

John

raddy · Post by **raddy** » Thu Apr 09, 2009 7:45 pm

notice what fuel he want tu use, than notice what is stoichio ratio of E85 and then they will be not so monster anymore...

chris2712au · Post by **chris2712au** » Thu Apr 09, 2009 10:31 pm

well unfortunatly that is probably what will come from running such large injectors.. and also you must have a rather large AFM as the z32 will only get you to 500hp I think.. then if you have a rather big cam maybe your idle will be 1800 - 1900rpm... not really good for a street car.. once again theoretically speaking you could use a fifth injector ? or dual injectors how you would control them in nistune I dont know... fifth injectors use to be the rage as they didnt have this too large problem however the setup was extremely critical to injector location as you have to get the extra fuel into each cylinder evenly... the result was to mount the extra injector a bit upstream of the manifold resulting in potential fire hazards but giving the ability to cool the intake air well... alternatively dual injectors could be a go as in 2 x 800 cc injectors you have a manifold pressure switch switching in the extra injectors at a certain boost level and halve the pulse width at that point... you could also play with the sizes like 1000cc and 600cc etc the smaller ones just in till you get on boost.. highly theoretical but if you want to play around..

also for your afm problem you can put in an un metered bypass surely the 3" will be a little on the shy side.. this again has to be triggered at a certain point.. this has the benifit as if it stuffs up things only get rich..

as for the pressure switch to activate the extra set of injectors put two in as if one fails the other one will be active cause if those extra injectors dont come in yep bye bye motor.. also check the loadings of the injectors on the ECU.. maybe the boys could comment on that for you.. but ensure two of everything so there is dual redundancy if a component fails..

I actually thought about using the boost control circuit for a fifth injector setup on the s15.. as it only needs a duty cycle does not have to be fired by the CAS..

Adam Hopkins · Post by **Adam Hopkins** » Fri Apr 10, 2009 11:05 am

I am just speaking from a honda background, but can you use an injector driver box? That will help to control the injectors much more precisely.

chris2712au · Post by **chris2712au** » Sat Apr 11, 2009 8:48 pm

Still thinking that the atomising of the fuel aka spray pattern wont be so crash hot at the smaller duty cycles with those massive injectors.. your going to get raw fuel running into the cylinders..

chris2712au · Post by **chris2712au** » Mon Apr 13, 2009 11:06 am

here is a thought how about dual nistunes... then you could run dual maf's dual injectors ??? it would fix all your problems... not sure if you can just pick up all the inputs in parallel I think some other ecu's have the option for sequential injectors.. but hey what a project.. if the mafs in parallel will give you enough of a stable voltage at idle to set up.. what engine are we talking about though ? RB or SR or Z motor..

John · Post by **John** » Wed Apr 15, 2009 2:10 am

Whow dudes your getting kinda crazy, dual Nistunes!!

Hopefully my engine will be redy to start at the end of this month or in the beginning of may, if the car can idle @900rpms no one will be happier than me

Regarding the Z32 MAF yes i have also heard something about 500hk. I know some DSM tuners that run a GM MAF which you also should be able to blow through and that had a bigger hk limit than the Z32.

Whe have people hear in Sweden who have gone as big as 720cc injectors on regular petrol and only used a SMT5/6 piggyback box to get fuel mixture right.

Regards
John

chris2712au · Post by **chris2712au** » Wed Apr 15, 2009 6:54 pm

there is a long long way from 700cc to 1600..

John · Post by **John** » Fri Jul 10, 2009 6:48 pm

OK guys and girls. I received my Nistune somewhat later than expected, big group buy here in Sweden so some things got a bit draged out.

Now fore the exciting bit. 1680cc injectors running E85 fuel. K constant @ 350 latency @ 700us and -10 in the fuel map (filtered values) im running lambda 1 on idle!!! I will get out on the streets and do some tuning under load this weekend.

The only problem Ive been having seems to be with the stock O2 sensor. when runing closed loop the AFR goes to leen and then to rich and back and forth I think it has to do with my big injectors.

Regards

John

chris2712au · Post by **chris2712au** » Sat Jul 11, 2009 2:22 pm

I would be turning the O2 off.... I think that you have made the point that your car is not going to be the most fuel efficient anyway... otherwise try moving it down the front pipe a bit... well done on the idle.. I really didnt think it would be capable... what is the injection time ms...

John · Post by **John** » Sat Jul 11, 2009 6:15 pm

At idle and around 14.7 the injector time in ms is abaout 2.1 -> 2.3.

Todays project will be to tune the fuelmap so that the Target AFRs match the AFRs on my Zeitronix.

chris2127au -> I was a bit worrie my self that this woulden work. And since the car seems to be running close to lambda 1 without the O2 sensor then i will probably leave it unplugged for now.

Cheers!

John · Post by **John** » Mon Jul 13, 2009 9:21 pm

After this weekend WOT tuning the car runs great on just 1.1bar turbo pressure. I had to add loads of timing on the top just to keep the EGT down, E85 burns much slower than gasoline so at the beginning i had almost 1250 degrees Celsius EGT, now with 15 more degrees timing on the top I’m down to about 870 after i have done a pull on 4rth gear.

Question here, does the timing in the log viewer show the correct value? I’m asking because according to that I’m running 35 degrees timing on top and that sounds like a lot!

Regards
John