Do I really need 550cc injectors??

[Cheks_Talon_TSi]

Recently I built up a new engine for my 1G DSM. My major upgrades were: 2G pistons 0.020", HKS cams, ported head with 3-angle valve job, 2g ported exh manifold, 2g ported 02 housing, Ported EVO III BIG 16G, mitsubishi multilayer steel head gasket, mbc, 3" downpipe with cutout valve that leaves fully opened downpipe, walbro 255 fuel pump, rewire kit, adjustable fuel pressure regulator, plus all the basic and free mods.

I am running with stock injectors and with the stock ecu. Yesterday we go to the 1/4mi race track. We are logging the engine with an innovate wideband. We set the fuel psi at 50 just to be sure we were running on the "safe side" since we haven't tested before. Almost all the 1/4 track the wideband was measuring 10.2-10.4 (rich) but as soon as the car reach 6500rpms the wideband reads 13.285 (lean) all of a sudden. It does the same in second and third gear at high rpms (between 6500-7000rpms) it gets leaner. BTW, i am shiffting at more less 6850rpm. My boost gauge is reading 14-18psi. My best time was a 14.555 @ 97.5mph

What can be happening with my A&F mixture??? I am running rich almost all the 1/4mi but just before every shit it gets leaner Should I bought a set of 550cc and adjust the fuel pressure at 38psi (as it should be)??? If so, will I be able to control the over flow of those injectors with my adjustable FPR?? or will I need to buy some kind of dsmlink or an AFC or what is the best option i have??? I already have an eprom ecu but still unsocketed.

Well I hope to hear some comments and suggestions from those of you experienced guys.

thanks in advance

sergio g.

 

[dsm-onster]

With the SAFC hiding 61% of your airflow, your engine would only see .39*50 = 19.5 lbs/min, which gives you 19.5*454/6500 = 1.362 g/rev. Your ECU would laugh and try to run 28 degrees of timing, and you'd see some ridiculous knock.

When ever my ecu laughs, something breaks

All the above is a great explination/info.

To add the obvious, the ecu has a map/memory that adds a specific amount of timing for a particular airflow. More airflow less timing. If you fool it into thinking there's less incoming air, then it uses a higher ignition time. This can be bad it that particular ignition time is too high for the ACTUAL amount of incoming air.

 

[jemsoccer]

To explain this for posterity (not necessarily you, but in case someone who doesn't know comes across this)...

The SAFC works by "hiding" airflow from the ECU. Therefore, if you hide enough airflow for 1150cc injectors, you would have to pull out (450/1150)-1 = 61% of the airflow. Given that the highest timing map is 2.1 g/rev (or 2.2 there's some conflicting info out there).

Now, assume that you take that big shiny turbo and you end up flowing 50 lbs/min at 6500 RPM, which is more than respectable. Without any airflow adjustments (DSMLink), you would see 50*454/6500 = 3.49 g/rev which puts you on the top timing map, and you would expect to see 16 degrees of timing assuming nothing else is pulling timing.

With the SAFC hiding 61% of your airflow, your engine would only see .39*50 = 19.5 lbs/min, which gives you 19.5*454/6500 = 1.362 g/rev. Your ECU would laugh and try to run 28 degrees of timing, and you'd see some ridiculous knock.

Looks like I have some research to do before I really get into tuning my car. I don't know what the hell he just said! LoL... I'll be figuring it all at very soon though as I will be installing an SAFC2 in my GSX next month when I finally get to put it all back together!

 

[2gGSX]

I'm willing to explain any portion of that you want. Quote that post and bold the parts you want a better explanation of if it's something you're interested in.

 

[90gsx16g]

To explain this for posterity (not necessarily you, but in case someone who doesn't know comes across this)...

The SAFC works by "hiding" airflow from the ECU. Therefore, if you hide enough airflow for 1150cc injectors, you would have to pull out (450/1150)-1 = 61% of the airflow. Given that the highest timing map is 2.1 g/rev (or 2.2 there's some conflicting info out there).

Now, assume that you take that big shiny turbo and you end up flowing 50 lbs/min at 6500 RPM, which is more than respectable. Without any airflow adjustments (DSMLink), you would see 50*454/6500 = 3.49 g/rev which puts you on the top timing map, and you would expect to see 16 degrees of timing assuming nothing else is pulling timing.

With the SAFC hiding 61% of your airflow, your engine would only see .39*50 = 19.5 lbs/min, which gives you 19.5*454/6500 = 1.362 g/rev. Your ECU would laugh and try to run 28 degrees of timing, and you'd see some ridiculous knock.

i love it.

 

[turboAWDfanatic]

(hopefully I'm not being repetitive here)...I didn't read all the post thoroughly, but I don't think anybody mentioned getting a modified chip as a cheaper alternative to the DSM Link. The Link is definitely amazing, but if you're on a budget you can get a chip from keydiver at dsmchips and install an AFC to fine tune the chip. Basically when you order the chip you tell him what injectors/MAF/rev limit, etc that you want, and he programs it for you. There is an option to eliminate fuel cut. Assuming you find a good price on a used AFC this saves some money and is a great way to go if you know what turbo/injectors/maf you're going to be running. If you go this route your stuck with the chip you order so you can't change your injectors or anything unless you order another chip (for a discounted price I believe). BUT, if you're REALLY interested in learning the chip you can go to the Yahoo group "dsm-ecu" and learn everything you need to know to program the chip yourself. At that point you can add a chip emulator like the Moates Ostrich which plugs into your ECU and acts like a chip. This allows you to swap between different chips on the fly, and with Tuner Pro it has a user interface that gives you GUI interaction w/ the ECU kinda like DSMLink (I think. I haven't tried it yet, but I know there's Tuner Pro definitions out there for the 1g DSM chip). This gives you tons of flexibility at a very cheap price...but DSMLink dominates when it comes to doing it fast and easy.

As stated before, AFC will only go so far. To put it simply, since it is lying to the ECU, your timing gets more agressive the more you lie to the ECU to compensate for bigger injectors. Push it to far and you get nasty detonation (you *can* get a good amount of power out of just an AFC before this happens, but you should have the capability to log knock before you try it). As you go higher you need to be able to control the fuel *AND* the timing...as well as get rid of the fuel cut issue. Either DSMLink, a modified chip + AFC, or (if you have lots of money) AEM EMS will all accomplish this for you. Its up to you depending on how much money you have much you're willing to learn about the ECU.

With that in mind, dig around ebay for a $15-$30 logging cable. They're available for laptops (w/ a serial port) or for Palm, but you have to get the right cable. Then you download a free logger program like mmcd or tunerstein. This will allow you to see several things...most importantly knock. You can also see what your injectors are doing.

Sorry for the long post, hope this helps rather than confusing you. Search function is your best friend here, and the dsm-ecu group on Yahoo has unbelievable amounts of info on the ECU.

Good luck!

 

[Cheks_Talon_TSi]

(hopefully I'm not being repetitive here)... Search function is your best friend here, and the dsm-ecu group on Yahoo has unbelievable amounts of info on the ECU.

Good luck!

I was just about to ask about that "dsm-ecu" Yahoo group. My brother told me about that group but I haven't search yet.

AS everybody said, dsmlink + a good set of inyectors is my best option but it is too expensive. I will make a bigger research and hope to get the money to buy the dsmlink and finally get my engine well tunned.

Thanks in advance

Sergio G.

PS: Does anyone of you had used the dsm-ecu to calibrate your engine??

 

[jemsoccer]

To explain this for posterity (not necessarily you, but in case someone who doesn't know comes across this)...

The SAFC works by "hiding" airflow from the ECU. Therefore, if you hide enough airflow for 1150cc injectors, you would have to pull out (450/1150)-1 = 61% of the airflow. Given that the highest timing map is 2.1 g/rev (or 2.2 there's some conflicting info out there).

Now, assume that you take that big shiny turbo and you end up flowing 50 lbs/min at 6500 RPM, which is more than respectable. Without any airflow adjustments (DSMLink), you would see 50*454/6500 = 3.49 g/rev which puts you on the top timing map, and you would expect to see 16 degrees of timing assuming nothing else is pulling timing.

With the SAFC hiding 61% of your airflow, your engine would only see .39*50 = 19.5 lbs/min, which gives you 19.5*454/6500 = 1.362 g/rev. Your ECU would laugh and try to run 28 degrees of timing, and you'd see some ridiculous knock.

What does the "g" mean in g/rev and what does it relate to? And the lbs/min deals w/ airflow? Thanks!

 

[2gGSX]

Well, g/rev means grams per revolution. It is another way of representing airflow, just like lbs/min is pounds (of air) per minute.

Lbs/min is used more frequently in terms of describing the output capacity of a turbo. G/rev on the other hand is actually a way to measure engine load and cylinder pressure. In common practice, lbs/min is what people use when they compare airflow (such as in an E-peen contest) while g/rev is primarily used when talking about the fuel and timing maps of an ECU.

 

[jemsoccer]

Well, g/rev means grams per revolution. It is another way of representing airflow, just like lbs/min is pounds (of air) per minute.

Lbs/min is used more frequently in terms of describing the output capacity of a turbo. G/rev on the other hand is actually a way to measure engine load and cylinder pressure. In common practice, lbs/min is what people use when they compare airflow (such as in an E-peen contest) while g/rev is primarily used when talking about the fuel and timing maps of an ECU.

Cool... Thanks!

 

[architechnik]

Quick note on the TunerProRT, there are not too many good definitions out there for the 1g. There are several for the 2g, but I have not yet found a really nice one yet for ours.

PM me if you end up going this route, as I have a basic one put together that has just the important stuff highlighted so far, ie. injector size, duty cycle (needed for certain brands), and airflow modifications (2gmaf on 1g).

I do not yet have the a/f mapping down in an easy format, but the dsm-ecu group has directions to locate and overwrite them if you feel so bold.