Bosch 3 Injectors longer crank times

I was not getting any replies at the Corvette forum...hope i get a better response here

Thanks in Advance

I was advised to ask around over here.....need tuning help now

Original thread here http://forums.corvetteforum.com/c4-t...ank-times.html

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Hey guys

86 Coupe
Cast Iron Heads
Stock L98

I noticed after i installed my Bosch III injectors it takes longer to start the car both cold and hot,,,, have to crank it for 2-3+ secs. it used to fire almost instantly (cold) and a little longer (hot) before the injector swap.

Fuel pressure is at 42psi with key on and holds for 2 hrs.
New Walbro pump--sock and newer fuel filter. Pressure is about 38 with engine running. Timing is set to factory at 6 degrees.
New fuel pump relay
New MAF burn-off and Power relay
New Iac
New CTS
New cold start switch (pricy?)
MAF cleaned
New PCV Valve
Throttle body removed and thoroughly cleaned
no vacuum leaks found

No fuel present or fuel odor in the vaccum line to the FPR

One thing i did notice is if i "bump the engine over" ever so slightly and turn the key back--then attempt to start it immediately a 2nd time---it fires right up.

Runs great after Either starting method---when i shut it down and leave it for 2 hrs or so---fires up right away (warm...not hot).

Does the swap from Mutecs to Bosch III require some sort of custom tune?

would appreciate your wisdom here

Thanks

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What kind of values are you putting in theses tables. i tried the arap6e bin in my car--disabled the CSI--Added and changed values of 1.00 all the way down to 0.20 many times back and forth in the first 8 cells that had zeros in them in the table Crank Fuel PW Multiplier vs. Ref. Pulse, and it still would take 3+ secs to start cold every time.

I put back my $32mask bin and was looking at the table Crank Fuel PW vs. Coolant Temp wondering how to change and what values i should input to try to increase cold starting times with the cold start injector hooked up.

Any info would be appreciated

Thanks

Ray
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This is the table i have and the present values in the cells

hmmm... just read that thread at the Vette forum. Those guys do like to complain a lot.
Anyhow, the boschIII injector has a slightly different performance curve than the multecs do. They are superior injector though. There are some tables in $8D (the one I'm familiar with) which address cranking fuel and I would assume that your mask has the same or similar tables.
Also what part number are the injectors? the Bosch number that is,not the GM or ford number, it will be 0-280-155-xxx, its on the side of the injector. Those injectors are used with at last 3 different pressure levels by GM and Ford. The flow ratings can sometimes get confused or misprinted.
Basically you just need to adjust your tables. There is also a low PW offset table that deals with low PW injector performance.
But the one thing that I noticed was not mentioned in your other thread is the actual injector flow value. It may be a little off, which will throw off the whole fuel curve.

Thanks for chiming in.
The injector number on my Bosch 3 is 0 280 155 700
I bought them FIC Injectors here http://www.corvetteinjectors.com/sho...p?productid=19

They are supposed to be flow matched at 22.9lbs.

I am very new to tuning but eager to understand that aspect.
Here are the injector offset tables i have in the $32



Also fairly new to wrenching but with the help of the guys at the Corvette forum, i have tackled and completed jobs on my car that before joining the forums i would never have dreamed about doing myself---a good bunch of guys with lots to offer as im sure holds true here also.

Ray

According to the list at witchhunter performance that injector flows 204cc (19.4lbs/hr) at 3 bar. The 0280155710 flows 210cc btw and can be found on the same Ford vehicles (I collect a lot of these from 4.6L SOHC Fords at pick-n-pull).

Is your chip programmed for 19 or 22lb injectors?
If you are programmed for 22lb injectors you can just up the fuel pressure to 4 bar (58psi) and you'll get 22.41 lbs/hr(235.55cc). Nice thing about 4bar is that you'll get better atomization, and those boschIII's work great at 4bar (thats what GM uses with them).

In a thread relating to this subject last year Rbob wrote;

In that same thread it was suggested that the low pulsewidth offset values be zeroed out. I've seen that suggested several times here, I will be doing that on the next one I build.
Also there was a question about how to figure the in between values on the table above. You can chart it out on some graph paper, do it in excell, or lookup the formula for a "piecewise linear interpolation table" these are used in computer programming all the time. basically it calculates the slope between the known points then you move along the slope the desired distance to get your value.

I just noticed above that you say FIC claims these 700's to flow 22.9lbs. Witchhunter says 204cc(19.4lbs) I find that interesting. Last year I ran 3 sets of these that I had just ultrasonic cleaned in my homemade flow bench. IIRC I was getting somewhere around 190cc at 3bar using distilled water (water and gasoline will not flow the same). I was just looking to match them up at the time and wasnt looking to determine the actual flow rate using gasoline.

But anyhow 19lbs and 22lbs are quite different.

Also just noticed that link to FIC about your injectors, FIC says they work for a 305 LB9 (which I believe had 19lb injectors), but above that they say they drop in a 5.7??? I think 5.7's had 22lb and 305's got the 19lb injectors. Someone please correct me if I'm wrong.

raiderz, once the engine is up to temperature check the BLM values. If high, say 145, then the injectors are most likely around 19 #/hr.

You are correct.

RBob.

Datamaster Scan---The BLM'S Fluctuate high and low while driving in closed loop---average in the 120's i guess----they get as low as 110 and high as 140 but settle back down relatively quickly.

Latest scan here if anyone wants to have a look at it
http://home.cogeco.ca/~raycook3/Corvette/86Corvette%2009_27_11.uni

I spoke with Jon at FIC Injectors and he assured me that my fuel injectors are 22.9 Bosch III at 43.5lb pressure at the rail.

Ray

I have changed a few values in this table and the car is starting in 1.5 secs cold and fires off instantly at any temperature when warmed up (almost scary)
This is my new Crank Fuel PW vs Coolant table in $32

Im gonna play with (increase) the values in the 4 cells from 25 to 90 degrees and see if i can quicken the cold fire. I might lessen the msec a bit from 111 to 239 to see what happens also.
I can unhook battery cable-- swap chips in the ecm and hook up negative cable again in 40 secs....LOL

i'm not trying to sound like a dick follow you from the corvette forum to here...

but since i use this board, that board, and several other boards...

ill just chime in my 2c.

a) I don't think injectors are bad...or need changing i think it's something else.

b) if you want to change something you need to fix your pw vs temperature tables...

A N D

b2) you could add in a few extra pulses on the pw vs crank multiplier number.

let me post you a screen shot of what I am talking about.... just a second.





this is the stock .bin file on a '91.
and the stock temperature .bin on a '91.

i would assume the numbers would be very very similar for any l98 series engine. DO NOTE: those are usec's. not msec's.

you could change table entries for the first few entries up to 24 crank pulses to 1. instead of say .... 0. then you will have injectors firing instead of on pulse number 20 or w/e pulse number it is....

that's why it either fires right up or after 2 seconds.