l2r99gst

iTrader: (2)

Actually, I run cams on my stock VIII pump and injectors. I have a IX pump sitting here that I haven't gotten around to installing yet.

Here's my input on the stock pump (IX pump) and injectors....they are both fine for the stock turbo. AMS did tests on the stock IX pump and their results show that the IX pump is capable of flowing enough fuel for the stock turbo. Of couse, this is depending on what AFR you want to run. They won't support a very rich AFR at max airflow rates. Let me explain...

The stock turbo will max out around 42lb/min or so. Now, this is pertty much MAXING out, not just your everyday airflow. Even on a max airflow run, most of your run will be below your max airflow. But just for information sake, let's see if the stock injectors are up to the task of meeting that airflow:

4*560 cc/min= 2240 cc/min
Gasoline has a specific gravity of about .74
2240*.74=1657.6 g/min
1657.6/454=3.65 lb/min

So, at 11:1, the stock injector can support:
11*3.65=40.15 lb/min

At 11.5:1, the stock injectors can support:
11.5*3.65=41.98 lb/min

At 12:1, the stock injectors can support:
12*3.65=43.8 lb/min


So, the stock 560cc injectors should be able to hold roughly an 11.5:1 AFR on a maxed out turbo. Of course, there are a lot of variables that go into the exact AFR, and this is maxing out the injectors. Some people don't like having maxed out injectors. Some people don't like having too big of an injector. There are two sides of the coin here and both have their good points and their bad points. I personally will not upgrade my injectors while keeping my stock turbo since I feel it just isn't necessary. However, when I do upgrade my injectors, I will do it once and buy large enough injectors to give me headroom for future upgardes or different fuels. So, I would probably go with 1000cc, for example.

I am not suggesting that you do what I do and not upgarde your injectors, but I figured I would at least show you the numbers for our injectors and turbo, so that you don't go rushing into an upgrade that isn't absolutely necessary. If you don't feel comfortable with high IDC% and want more headroom for future upgrades and to have peace of mind, then get the bigger injectors. They will definitely give you more room and allow you to not have to worry about injectors running at 100% IDC, but depending on your intended AFR and airflow numbers, they may not be needed.


Eric

Jack_of_Trades

iTrader: (17)

Well, I will toy with my AFR's and see if I can slightly lean out my tune to bring the IDC's down. I still think a bigger injector maxing out no more than 80% IDC will atomize better (rather than pooling behind a closed intake valve running 100%IDC's) will produce a more reliable tune. Since Alky injection is already in my mod future, I will just add that before injectors since it will help me to reduce my IDC's by design.

Tomorrow I am installing my pruven fuel pressure adapter plate so I can see how well my fuel system is supplying the correct fuel pressures.

l2r99gst

iTrader: (2)

That is a big reason why most people want larger injectors, and I agree to a point. I think the 80% number is thrown around more as a 20% haeadroom to allow for all of the variables,ie temperatures, fuel pressures, etc, and still be safe.

Even at 80% IDC, the injector is held open for 80% of the engine cycle, so the majority of the fuel is being sprayed while the valve is closed. So, I really don't think the reliability of the tune is going to be affected in that respect. Also, you have to remember that your max IDC isn't the whole run, but only a fraction of it.

By no means am I advising against bigger injectors. Actually, I would recommend running as big as you feel comfortable with. It's just that I see a lot of people wasting money upgrading injectors several times, when in some cases, it isn't needed.

The biggest issue with really big injectors is of course idle, but with our abilities with ECUFlash, most of those issues should be resolvable.


Eric

coolguycooz

hey l2r99gst i was wondering for that formula where did you get the 454 number for the formula.

Also i just installed the walbro 255. All i can say is WOW YAY I am happy. I went from a maxed out AFR of 11.8 or so to an instant 9.9: 1 haha thats almost 2 full points richer. I havent gotten a chance to go out and fully return my car yet.

All i know is all evo 8 owners should get a walbro 255 if they run anything over stock boost in the upper rpm range.

After doing the walbro 255 install, it made me wonder why the 8s didnt come with a higher volume pump from the factory, In my particular case runing 21 psi falling down slowly to 19 psi by the time i hit 7k rpms. That made my IDC hit 100+%

Walbro255= The first mod any evo 8 should get PERIOD.

l2r99gst

iTrader: (2)

454 grams = 1 lb

The Walbro isn't necessary for a stock turbo. An Evo IX pump would do fine. The VIII pump sucks because of the pressure relief valve.

If you haven't seen it before, here is the graph from the AMS test:


Eric

Slo_crx1

iTrader: (9)

Reading this confuses me about my '03 Evo...yesterday I took out the restrictor pill and now I hit 23psi peak (roughly, it's not off a map sensor so it's more of an estimate) and settle to 19psi through the top-end of the rpm range. Even in 5th gear I hit a max of 21 and hold a steady 20 from there out, and my afr's once I reach over 18-19psi never come above 10.8 for some reason. I'm assuming it's still the stock pump though (I bought the car used so who knows) and it definitely has the stock injectors still.

mandy1

iTrader: (1)

i ran 11.9 with 375hp using stock evo8 pump on meth 375ml nozzle,afr was in the 11.5-11.8 at 22psi.

Jack_of_Trades

iTrader: (17)

Well yeah, alky injection obviously takes the strain off of the fuel pump since you now have 2 fuel sources and can run leaner with alky injection usually.

Mellon Racing

iTrader: (38)

I have plenty of customers with EVO8's with raised boost, air filter and turbo back exhaust and even one with a FMIC and header on the stock fuel pump and not going lean.

that being said, it's best to get the fuel pump done first since you're going to need it eventually anyway especially after cams/turbo etc..and you'll need to be tuned for it.

nj1266

iTrader: (6)

I agree with Eric and AMS and KevinD that a Walbro is totally unnecessary for an Evo 9 with basic bolt-ons. My 9 has a TBE with test pipe and LICP. I had a Walbro that I bought a while ago sitting in my room collecting dust. It was intended as a spare in case the Walbro on my Evo 8 gave out.

On Sunday my friends and I installed it on my Evo 9. Then I logged that car today at the same time and same palce that I did before the Walbro. The pump did not make much of a difference on the 9. I was hoping that my IDCs will drop significantly, but not a lot happened. The AFR did not change much. Only a slight change between 7000-7500 rpm.

Here are the charts:

before walbro:




AFR and IDC after Walbro:




I am begining to think that the way we calculate IDC for the EVO is erroneous. A lot of us are running around with close to 100% IDC and we are still able to lean out and richen the AFR at will. I believe that John Bradely's and Tephra are correct and we need to use the scaling of the injectors to determine IDC rather than use injector size.

Mellon Racing

iTrader: (38)

good illustration nj... that goes along with the minor correction I'm doing for EVO9's with fp upgrades.

coolguycooz

Hey l2r99gst thanks for that graph, that was really helpful. Now here is the weird thing in my case. Yes i understand the evo 9 pump is significantly better than the evo 8. Well i have an 8 and my problem is weird because i have been runing 21 psi and 19 to redline for a good 4-5 months now. And my AFR problems happend over night. I was fine at 95% IDC until one day i go out and get a tone of knock and realize my AFR's are going lean. im like oh crap well ok time to richen them up. Well i go to richen up my fuel map, but the AFR's stay the same. So i am like WTF? well i keep on adding fuel until my IDC hits 105%. So i was like wtf is going on, i checked the vacuum/boost source to the stock FPR. everything was ok. So then i said it could be the pump, sure enough the walbro 255 fixed it.

Now my question is, why did the efficiency of my pump just go out over night? I would think it would be a gradual decay over a long period of use. Instead it literally happend over night. It is still bugging me, i fixed the problem, but i want to know what caused my old pump to just go poopy on me over night, assuming it was the old pump to begin with. The strainer on the stock fuel pump looked amazingly clean, nothing clogged. no big piece of poopy could have gotten in to the inner turbine of the pump.

AND

I narrowed out the possibility of colder temps causing my MBC to boost slightly higher. Plus i could have swore at one point in time i was runing 22 psi and still dropping my AFR's down to a flat 11:1, and 2 weeks ago i couldnt get them to go below 11.8:1 at 20 psi. WTF MATE???

the mystery of the poopy 8 fuel pump???

Mellon Racing

iTrader: (38)

my guess is that the stock pump was failing on you, it's the only thing that makes sense with the given information.

I bet if it were installed on a friends car with a stock pump and wb02 you'd see him lean out too (but don't try it of course)

coolguycooz

Yeah, that would be my guess too. This is a perfect example as to why investing in a WB02 is the first thing anybody should do PERIOD PERIOD.

That sucks because my 05 only has 17k miles on it.

Honestly i am almost tempted to do that to a buddies 8 hehe just so i can finally sleep at night knowing what exactly happend.

Mellon Racing

iTrader: (38)

yeah I'm with you there...I don't like replacing parts for no reason and also like to know the cause of failure before I do.