Ah, Megasquirt! I have one running in parallel 'monitor' mode on the Crossfire at the moment, so also have MegaTune. I've actually sent a box of tricks to HDDP for him to hook up to his motor as a starting point on this this. It's already looking like we may need to build a bit more intelligence into it though to make it behave like a proper 02 sensor. I'll post up more details as things unfold.

 

Reading the service manual suggests that it might be tricky to fool the ecu - seems to be 1,001 different ways to activate an MIL light and store a fault code.

 

OK guys,

I've been following this thread and now I'm wondering what the correct BOSCH injector upgrade part number is.

Is it the M-Benz injector for the CLK/SLK version of the W112 3.2 V6?

If you just drop a six-pack of M-Benz injectors on a stock Crossfire N.A. motor will you see any power increases ? Or will the MAF and O2 sensors just tell the PCM to reduce injector duty cycle and put you right back where you were ?

My last attempt at modding a "modern" MAF/O2/PCM set-up was a '97 FoMoCo 4.6 V8 SOHC "Mod Motor". Upgraded the exhaust, throttle body, larger MAF and PCM tune but topped out at 250 Hp because the 19 Lbs/Hr injectors were starting to "max-out". The later "product improved" Mod Motors featured 24 Lbs/Hr injectors and were good for 300 Hp.

I know I'm comparing a 4.6 V8 to a 3.2 V6 but to produce "X" amount of power you need "Y" amount of fuel. So I don't think you can ever expect to top 250 Hp using 17 Lbs/Hr injectors.

So...swap in a bigger set of injectors and let us know what happens !

Cincinnati Slim

 

Yeah, I gave him the info to put into his database... Now, I'm just waiting on the specs for the SRT6 injectors to arrive from Bosch.

 

Tireless as usual in your endeavors to promote the Crossfire HDDP. Not fair I thought someone else had done something and I had found it!

Anyone got any comments on the injector sizing calcs?

Notice that at 6,000 rpm, you have 100 revs per second, 1 firing per 2 cycles, is 1/50 of a second or 0.02 second for two strokes. Injector open time is 0.017 with 20 lb injectors (80% duty). Seems to add up to 100% duty with 17 lb! ie injectors open all the time?

Just goes to show how little benefit sequenced injection is once you get to the higher rpm's.

Malcolm

 

MALCB, It just happened that Stan Weiss has a brother who owns a Crossfire and is also is a member here... Stan could not find specs on our injectors either... I just happened to recently develop a relationship with Bosch and they are trying to get us all the info we need... But this is a slow process because Bosch USA does not get much info from Bosch Germany...

 

The way I see it is your right. When running in closed loop the O2 sensors will feed back and the injector on time will be cut, but acceleration is usually (always?) open loop, particularly as the Crossfire has narrow band sensors and can't control AFR. Larger injectors will flow more fuel during acceleration - that doesn't mean anything will happen quicker though, we would need to see the car run with AFR logging to know if more fuel would help. Other issues might be overfueling at cold starts when the system is open loop until temperatures rise, perhaps damage to CAT converters etc.

If the duty cycle is over 80% at full power that is unusual and reducing the duty cycle would help control fuel supply.

Malcolm

 

So perhaps someone could try a set of M-Benz CLK/C class injectors from the 3.2 on a Crossfire and see what happens on a wide-band o2 sensor. A good functional junkyard set would be worth testing. If there's no gross over fueling during open loop conditions it might be an easy way to pickup a little power on WOT runs and get a little duty-cycle "headroom" to allow for future mods.

Slim

 

I finally got the specs on the SRT6 injectors from my SPY at Bosch I must say, they have a HUGE flow difference from the NA engine and now I have to figure out how the SC engine is regulating the flow, whether by pulse width or pressure regulator.

NA ENGINE: 17 lbs/hr at 3.8 Bar, or 55 psi/ 14.5 ohms.
SC ENGINE: 51.6 lbs/hr @ 55.1 PSI / 14.5 Ohms based on 380 kPA = 3.8 bars = 55.1 PSI

But, this leads me to wonder if the NA engine would benefit from an injector swap...

 

HDDP,

It could be a combination. Do you need me to take a fuel pressure reading on my SRT6? (have to get a gauge) I forget whether this has been done on an SRT6 yet.

If the SRT6 has the same pressure and the pump voltage is not being changed during engine operation, then I would conclude it was only pulse width that was being change.

Good info!

 

No need to get the fuel pressure... They are all running 55-60 PSI... What would help is if you could give me the product numbers of that pump that sits on the driver side wheel well... My Bosch guy says that the 508***** part number is usually fuel related... But as usual here's the response...

"The part number you gave me, which must be missing the first 0, is fuel related. The 580 designates that it could be a fuel pump, pulsation eliminator, or a regulator. It is another number that we have never sold in the US and has not been established in our computer system".

If you can give me the MB part number, I can cross reference it with my MB parts wholesaler...

 

The one that is in the front? Looks like some kind of air pump? or are you referring to the rear wheel well behind the interior trim?

Just let me know.

 

The one in the front that looks like an air pump... I didn't know about the other thing... Perhaps it would be easier if you just gave me the page number of these items in the SRT6 service manual and I'll try to track it down from there...

 

I think I found the info on the pump up front... It looks like it is the "Charge Air Cooler Circulation Pump". But, that is not the item I was questioning, This device is located on the front edge of the driver side wheel well inside the engine compartment and is a round black pump looking device that has the Bosch part number 0580000021 stamped on it... But if I recall correctly, there is a Mercedes Benz part # also stamped on it... That is the number I need to identify the part since Bosch US has no info on this part...

Thanks in advance Jody...

 

If you check the HP per injector rating the stock is barely able to do 215 hp, but 50 lb on 6 injectors is good for over 400 hp!

I take it you mean is the SRT fuel pressure adjusted to accommodate the boost pressure? If those flow figures are right I would be looking for a fuel pressure regulator with a manifold "vacuum" pickup. I would say the fuel pressure at idle / no boost has to be much lower than 55 psi or it wouldn't be possible to make the injector duration short enough to have control of low fuel inputs, opening times of 1 ms don't work well.

Reducing fuel pressure with a high manifold vacuum also leaves some headroom to increase the pressure as the boost comes it - without needing a new pump and further increasing an already high fuel pressure.

If I had time I would put a scope on an injector - problem is I have hardly seen the Crossfire in two weeks because work is so busy.

 

So the SRT runs an air to liquid charge cooler - interesting, I assumed it was the usual air to air intercooler. Wonder how much the pump is and what it's capabilities are.

(Sorry not on topic but interested).

 

Why is work always interferes with the fun stuff! I'll hook the scope up on mine sometime this week and get some traces - typically someone has 'borrowed' my nice Fluke storage scope, so I'll have to record it all manually with the analogue CRT.

 

Ok, while you genius' hook scopes up to things and build GIZMOS for me to test, I'll be picking-up my new SRT6 engine on Saturday and scratching me head trying to figure out how to get it running in my car...

At least I will have some SRT6 injectors that I can install on the current engine and see what happens... Could be another fun little experiment attached to Woody's GIZMO...

 

PS: that device I was referring to, turns out to be the secondary air pump... It just has a different design and mounting location from the NA Crossfire... Funny thing, it's one of the many devices that were useless to my engine operation and Woody convinced me to toss it in the trash...

 

How come you get to do all the fun jobs.