jdm-v35

iTrader: (7)

planning to install 750cc injectors and tune with cobb accessport. just wondering if anyone has experience with scaling in with the accesstuner race software for injectors this size?

Just want to make sure Cobb accessport can handle it and will not have any problems running.

Also would like to know how the calculations are done for the VQ35 as I have seen the subi and GTR calculations but they are different and I have not had a chance to try using accesstuner race yet.

any help or advice for this would be appreciated.

bealljk

iTrader: (13)

Can only assume you're running FI? You may want to list your modifications…

I'm not a huge fan of Cobb but that's not to say it's an inferior product -

jdm-v35

iTrader: (7)

Sure! I posted my components in my Fi forum thread but figured the tuning forum would have more insight about this specific problem.

I have an 03 5at G35 at 60k miles and have had a couple previous FI setups but have not gone above 440cc injectors/walbro 255 on this platform yet so i'm not sure if I will have any issues with my next planned setup.

I have all the FI parts on the side right now and have not installed them.

Procharger at 9 psi (26/39 pulleys)
supporting engine mods:
RC 750cc injectors
treadstone 340lph fuel pump
5/16 motordyne spacer
stillen HFC
M2 3" HR y pipe
oem midpipe and muffler
Cobb Accessport
OEM plenum/runners with all castings smoothed out
transgo VB mod and trans cooler

maybe a Return fuel system.

many suspension mods/no exterior mods

I plan on aiming for 400whp with this setup and do not plan to ever go for more than that. Just wondering if I will be able to scale the 750cc injectors using the Cobb and get it to idle smoothly and run nicely at partial throttle.

I know a lot of people don't like Cobb but I have had it for like the last 4 years and I have the accesstuner race software already so I would prefer to use it if possible.

djamps

iTrader: (1)

It'll 'work' without a return style fuel setup, but it's not optimal. The return system aids in getting the tune more 'dialed in' (fuel system automatically compensates for boost) and also equalizes flow between all injectors. Without the return setup, you'll have a far bigger pressure drop across the injectors and the ECU has to make way bigger swings in fueling...there's a reason factory FI setups use return style. Basically if you wanna do it right get a return system.

jdm-v35

iTrader: (7)

Sounds good. I figured that a return system would be beneficial due to rising rate fuel pressure. I just wanted to make sure that the Cobb will in fact be able to scale 750cc injectors properly If I lower the fuel pressure to about 40 using the fpr. I just want it to be able to run smoothly and idle correctly without raising idle speed much.

djamps

iTrader: (1)

A fuel return actually helps immensely the ability to scale injectors since you don't require as small of IPW at low loads (far lower fuel pressure than stock at idle/cruise). As I mentioned earlier, the tuning benefits are huge not to mention the reliability.

jdm-v35

iTrader: (7)

Yea through my research I figured it would definitely help with that as I will be able to maintain stable idle fuel pressure.
Just pieced together/bought my fuel return setup so im good to go!

using cjm fuel correction, sard fpr, 6an lines/fittings, and dynotune fuel rail adapter to tap the driver side rail while being able to still leave the fuel damper on.

Thanks for the info. Hopefully I will be able to have a reliable setup that runs smoothly all throughout the power band. not looking for massive power.

btw djamps you have replied to my older build threads before. I had the JWT 700bb kit and I ended buying everything for a reliable build, left it at the shop, and went on a trip for over 2 months, came back and they didnt even touch it so I lost interest and sold the kit to the user you all know as "Eno" and parted out the rest. Just figured i'd update so no one thinks I blew the car up due to improper build since i didn't continue the thread only due to pure loss of interest. No noob mistakes!

djamps

iTrader: (1)

Ha! no problem. I have fuel returns on both my VQ's (one has 440 and the other 600cc injectors). I wouldn't want to tune a F/I VQ or especially rag on a F/I VQ without it.

jdm-v35

iTrader: (7)

Also was just curious about your tune. I notice in your sig it says self tuned. I figure due to lack of tuners i might need to self tune mine. I figure with 9psi pulleys ill be aiming for -5 degrees timing at the top for safety. Also how long did it take you to dial in your tune?

Only other car I have tuned was my supercharged maxima back in like 06 but I was using emanage blue. But I have been reading some of the tuning threads here and it seems it shouldnt be too much different. I guess ill have to think about whether id rather do it myself or pay an "ok" rated tuner locally.

djamps

iTrader: (1)

Superchargers are alot easier than turbos, especially with a fuel return. So if you know how everything work (timing, fuel mixtures, reading logs, doing 'safe' pulls) you should be fine. After you get your idle and part throttle tune good, pull a bunch of timing on the right and do a 1st gear pull to get a ballpark on your A/F, tweak the fueling accordingly, once fuel is 'close' go on to 2nd gear...wash rinse repeat. I wouldn't run more than 16-17 degrees peak at WOT in boost if you want to be 'safe'. You'll find VQ's retard in the mid range and ramp up with RPMs so a dip to 10-12 degrees in boost is to be expected around 3.5-4krpms, while it steadily increases to your peak at readline. My 'street' tune tops out at 18 degrees and dips as low as 12 degrees in the mid-revs. My race map goes to 22 degrees but requires octane additive to keep pinging to a minimum. Another thing you'll notice is these engines like to ping. If you get rid of every trace of ping, you probably wouldn't ever make more than 350whp. One more tip is to tune your fuel using the MAF table instead of the fuel table. It makes timing way more stable and helps prevent hesitation going in boost.

jdm-v35

iTrader: (7)

Nice thanks that really helps. I will probably go with safe timing and max it at 17 since we only have 91 octane readily available and I only plan to use it for street use. I will definitely remember to use the MAF table aswell instead of the fuel table. I used the fuel table on my emanage before and it definitely was a lot of trouble.

I figure get the idle right by playing with fuel pressure on the FPR and then adjust the injector multiplier in COBB and then do maf/timing table adjustment from there.

I hope I can get close to 400whp at 9psi even with a safe(17 degree max) timing map. Since these engines like to ping, how do you know when to cut back timing then? Do you do it based on the torque curve only?

I also have an AEM wideband and fuel pressure gauge in the car which will help monitor A/F during tuning.

I am on a trip right now and will be doing the install when I get back in a week or so. I have only used the emanage before, and have yet to try out the accesstuner race software. Hopefully self tuning will not be too difficult with this setup.

jdm-v35

iTrader: (7)

So I did my install and been working on self tuning for now just to get the car running smoothly.
FI Setup I ended up with:
procharger with 26/39 pulleys
RC750cc injectors
custom RFS using 6AN lines and sard fpr
cobb accessport
defi boost gauge, AEm wideband, greddy fuel pressure gauge

I have been working on getting the car to idle and start up nicely. I still have some intermittent hot start issues but have been working on maf calibration/injector scalar numbers to get it pretty close but am still fine tuning it to startup nicely and reliably.

*edit* I am pretty close now and have not done enough testing/driving yet but cold and hot starts seem great now. I will test it out a few more times just been playing with MAF tables and adjusting using live tuning/monitoring in accesstuner race! really loving the cobb and it seems very easy to use and capable. I just wish they listed ignition tables in actual degrees of timing so it would be a lot easier to adjust rather than using generic increments and using live monitoring to test.

pulled some timing in the 4800+ rpm range but have not really got that far in testing it yet since I want to work out starting issues first. Fuel pressure I have been playing with during the tune and keeping it in the range of 38-45 psi adjusting with each tune change to dial it in as smooth as possible and close to stoich.

*edit* got it running/starting pretty smoothly at idle at 38psi fuel pressure.

Is it normal for idle A/F on this car to swing a lot? It seems to be swinging constantly between 14.5 and 15.3 with random spikes to 16 sometimes. Or is it possible to tune it to stay constantly around 14.7 at idle? this is an 03 G35 so i know it doesnt have oem widebands and Im guessing it can't accurately dial itself in. Also im guessing idle will be slightly rough due to the supercharger circulating air to the maf even at idle.

unfortunately in accesstuner race it seems that they only list ignition maps in "increments" not actual degrees of timing pulled So I will have to watch A/F and knock and timing in live tuning and tune carefully.

As djamps said I have been working more with the MAF table to simplify things rather than fuel tables and it seems to be working out well.

jdm-v35

iTrader: (7)

guess it was just a matter of time till it happened to me aswell.. seems the cobb may have possibly bricked my ECU.. the fans will stay on constantly when car is in ON position and I am unable to get the AP to reflash it. I am trying the ecu power disconnect to see if it works in a few hours but if it doesnt I hope cobb will be able to help. I sent them an email and hopefully in a few days they will reply. The AP has great functionality but this happening is a big disappointment.

djamps

iTrader: (1)

The one time it happened to me with Uprev, I disconnected the battery for a couple hours, reconnected then it allowed me to flash. However from everything I've heard when this happens on COBB, you have to mail them the ECU.

jdm-v35

iTrader: (7)

yea i tried that and it didnt work. I think uprev works like that because they built it into their program to pick up where the crashed reflash left off but cobb didnt develop it as well. I ended up mailing the ecu to uprev to try and work on and I bought an osiris tuner kit, so I will be working with that later. It should be a little better to use for bigger injectors too since they have the warm start enrichment adjustments too.

jdm-v35

iTrader: (7)

got tuned and figured I would share my results from the dyno tune. car hot and cold starts like stock and everything is working great so far.

I am debating on upgrading to 12psi pullies but still not sure yet as I don't want to compromise the engine.I drive casually everyday though and never push it so I think it would be ok.