hello, so i installed my own version of a rear mount turbo kit ( which came out pretty good ) and after working out all the small issues i was ready to get it tuned. I have the cobb accessport to do that so i called efi logics in bethel ct and set up an appointment. I tell them i have all stock fuel setup and only want to tune for what it can handle. I get there (1.5 hr drive), and chris (their tuner) immediatly tells me that I need bigger injectors (550-600cc) for any boost even as low as 4 psi and that my stock injectors wont handle any boost what so ever. Also he wasnt sure if the pump was good for any type of boost as well. So they emmideatly pull my car off and send me on my way. 1.5 hr drive by the way lol. So i'm not saying that they r wrong or right, but if anyone has a professional 2nd opinion regardless on whether they r right or wrong please share with me. All im looking for is sub 5 psi safe tune. I also have the innovate LC-1 wideband. How many psi will the stock vq35de 03 g35 support? thanks

 

MAF/injectors both max out around 4.7psi if i'm not mistaken.

If you are boosted though, you should upgrade injectors. Fuel pump you wont need to at the boost levels you're planning on.

 

thanks for the reply, where did u get that information if u dont mind me asking?

 

Stock MAF should hold up to ~380whp dynojet (I've seen as high as 400whp). This is around 6 - 7 psi depending on a lot of things.

Stock 380cc injectors with no fuel system mods is your main issue issue, you're probably limited to 2-3 psi before danger zone at redline.

You either need an FMU to boost pressure above stock or an upgraded pump and a return system (ideally).

So... here's what I'd do if I were you.

*440CC-600CC injectors
*Walbro 255L/H pump
*Return line

With the return line, the 440's will be good to about 10PSI and retain more stock-like part-throttle and startup, with the 600's a little more difficult to nail down startup / part throttle tuning but with much better safety margin.

 

thanks for the feedback, if i get the 600cc deatchwerks injectors and a walbro fuel pump and not do the fuel return line - u think that itll b enough to have it tuned to 5psi and good drivability as a daily driver? im glad the stock MAF will get the job done.

 

Well, there's a catch 22.

I would NOT recommend running the stock MAF without a return line. In fact I would recommend it for just about any amount of boost on any platform without a return line.

The return line will increase fuel pressure with boost so the affect of maxing out the MAF is minimal, and the tune will be much more smooth and reliable. Without the return, if you get close to or actually max out the MAF (boost spike, cold weather, poor tuning, ect), you're going to be in big trouble.

 

man ur just full of good news lol, thank you for ur feedback though i really appreciate it, apparently im further away from completing this upgrade then i thought. I guess ill have to do all of this before getting the car tuned. I see that your profile says u tuned ur own car. I wish i knew someone around my way who could show me how to do that. I've been reading up on it but cant get any good instructions. This place I went to r actually being extremely rude and i was gonn buy the injectors from them and have them tune it but now that they've showed me the types of people they are i changed my mind. You wouldn't happen to be anywhere near CT area would you?

 

im looking at these turbo kits that they sell for this car and none of them come with a MAF upgrade or a fuel return kit, they only come with injectors, pump, and a flash. how come?

 

HAHA more bad news!

Uprev prices their products to discourage me from helping others unfortunately. Basically since I'm an end user you need the full tuner license ($700!). Most shops charge $700-$1200 for the full tune including license but then they hold the key to the tune and only they can mess with it. Really lame tuning scene for our cars which is why I said fawck it and did it myself. I got full rights to my own ECU (as it should be).

 

i dont have uprev i hav cobb accessport with the race tunning software. i can adjust anything i want i just dont kno how lol. i was gonn pay efi logics but their poor customer servise skills changed my mind. im on a budget here, and all these extra parts for only 5 psi sound like over kill man. im not a pro by far, but im not looking to squeeze every last pony out of my car i just want a safe tune for w/e the car can handle u kno

 

You just need fuel mods, bottom line. Whether it's an FMU like the JWT kit provides (hack IMO), or proper return setup. Regarding an upgraded HPX MAF, I had to spend hours tweaking the MAF calibrations after swapping it out to get startup and part throttle back in check...pain in the ****. So don't assume swapping the MAF out is the cheaper/easier solution than a proper fuel setup .

You can get by with just the Walbro and some 600CC's... but those huge injectors are pointless if the ECU can't read enough air (maxed out MAF) and/or the fuel system cannot compensate for for unexpected boost or maxed MAF (return line). Bottom line... no return line, you better get a champion tuner because there is ZERO room for error both in the tune or from the the kit itself malfunctioning.

I'll be straight up and say that Uprev/Cobb without a return line or some kind of fuel pressure boost reference is inadequate for boost tuning. There simply isn't enough resolution in the fuel tables while in boost for proper tuning. For example on my Uprev pretty much only two columns out of 16 cover the entire 1-10psi boost level at almost any RPM...without the return line the A/F would be all over the map in boost. And uprev is pretty much identical to cobb in terms of the way things work... they are both just tweaking the stock ECU after all.

Using a UTEC with MAP (pressure) sensor reference you would be MUCH better off without the return line than Cobb/Uprev, since the tune would be tailored to each PSI of boost rather than the sketchy MAF reference. So my recommendation to you is that if you want to skip the return line and HPX MAF go with a UTEC or full standalone, and don't play games with flashing your stock ECU.

In fact, UTEC would be BY FAR the safest option with overboost cut and knock detection, and you won't have to upgrade the MAF or get a fuel return if you don't want to.

 

ohh yea, i read in the manuel that it can callibrate the maf, im still using the stock maf housing so i dont think it will need calibration but i donno. id get the injectors and the pump if that would be it, but again theres like noone around here to tune using cobb. ill need to search long and hard, unfortunatelly. in this fmu, does the signal hose connect to the charge pipe?

 

i decided im going to go with a jwt fmu kit, they told me it'll b enough to not have to do injectors. let me kno if u agree.

 

Should be. It's just cutting things real close, those injectors will be at 100%. I wouldn't dog it too much.

 

i c, i'll deff take it easy, i dont race my car anyways just did this to have a lil more pull on the highway. hey u've been a great help, just want u to kno that im very greatful. hope its ok if i keep getting advise from u like this in the future