Can I use the Bosch CNG injector for LPG?

Propane, Butane, LPG, GPL, C3H8, C4H10
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kikkegek
Posts: 415
Joined: Thu Nov 17, 2011 2:12 pm
Location: Netherlands, The Hague

Can I use the Bosch CNG injector for LPG?

Post by kikkegek »

hi everybody,

I successfully got my 454 big block up and running LPG vapour injection. Runs really well. I am currently using 2 ohm LPG injectors and a peak&hold board to drive them.
[ur]http://www.facebook.com/77suburban[/url]

I am helping others now also moving into LPG injection and looking for parts. Somebody pointed me out that using the Bosch 2200cc injector could make the peak&hold driver board not needed. BEcause they are 9 ohm.

this is the injector
https://www.bosch-motorsport-shop.com.a ... ector~4317

The data even says they were developed for CNG (gaseous fuel).
Bosch_2200_CNG.jpg
I contacted Bosch for flow information, because although developed for CNG, they only share gasoline flow rates (kg/h or cc/min) and not the l/min expected for LPG and CNG injectors. But so far no help.

So I though I'd give it a shot over here.

Who knows and tried these injectors?

And if it can run CNG would it also be fine to run with LPG?

best regards,
Jochen
storage/project: 1974 GMC 25HUNDRED Suburban - fresh rebuild 350 small block - TH350-NP203 - 4.10 gears - IMPCO425 mixer
driver/project: 1977 GMC C15 Suburban - 454 big block - 4L80E- LPG VSI - 3.08 gears
sold: 1986 Chevrolet Suburban K20 Silverado

kikkegek
Posts: 415
Joined: Thu Nov 17, 2011 2:12 pm
Location: Netherlands, The Hague

Re: Can I use the Bosch CNG injector for LPG?

Post by kikkegek »

cause I cant find any info on applications and Bosch doesnt seem to know their own shit (1st line support only sents me whats available on internet)...I did some calculations of my own.

Maybe somebody can confirm or correct?

Bosch 2200cc injectors
flow 8,65kg/h (CH4=aardgas) = 19lb/h
based on gasoline and 100% dutycycle that results in 40hp per cylinder
LPG results in less hp per cylinder, so I guess not interesting for our big engine applications?
WhatsApp Image 2022-03-25 at 7.33.16 AM.jpeg
storage/project: 1974 GMC 25HUNDRED Suburban - fresh rebuild 350 small block - TH350-NP203 - 4.10 gears - IMPCO425 mixer
driver/project: 1977 GMC C15 Suburban - 454 big block - 4L80E- LPG VSI - 3.08 gears
sold: 1986 Chevrolet Suburban K20 Silverado

C3H8
Posts: 1095
Joined: Fri Sep 09, 2005 11:23 pm
Location: Winnipeg, Canada

Re: Can I use the Bosch CNG injector for LPG?

Post by C3H8 »

Volume wise they should be ok. Their pressure is rated at 3 bar. Considering LPG has twice the BTU's and most LPG regs put out 1 to 2 bar the volume should be within the working range.

The difference in ohms is another matter. As you stated the typical LPG ECU drives a 2 ohm injector, however LPG injectors typically come in a range of 1.5 ohms to as high as 4 ohms. Gasoline injectors are another matter. They can range from 1.7 ohms all the way up to 16 ohms. If your going to drive them off the OEM ECU you would have to be very careful to make sure the gasoline injectors and LPG are a similar rating. Even knowing that, the difference in the liquid gasoline vs the vapour performance of the LPG/CNG injectors would be substantial. I'm pretty sure if it was possible the manufacturers would have figured out the correct sizing.

I guess the question is "where are you actually trying to go with this". I ran a 3.5L V6 Chrysler right off the OEM computer back in 1996/97, however we had to use vapour off the tank and regulate it at about 70 PSI to get enough volume through the injectors. There was no convertor available that could put out that pressure. We were using Bosch injectors but I can't remember if they were rated for LPG. I don't think so. I think they were just a high flow injector compared to the OEM gasoline ones. We just used a relay to turn off the gasoline injectors and turn on the LPG. This actually worked well as long as air temperatures remained high. Fuel trims and everything were quite good. I probably put on 10 or 15K km's during the summer months, however any cold weather reduced tank pressure to fast to keep up with a 70 PSI requirement. It was just an experiment. During that same period we were experimenting with very early injection systems until the major manufacturers decided to get into the market. We worked with two or three local companies that had designed ECU's to work with lower pressures, however we did not have the resources to actually get them to market. The procedures and costs were brutal.

The systems did work though and they were plug and play. No ECU needed although it became apparent that an adjustable ECU had specific advantages once they came on the market. One of these systems actually made it to market as a diesel enhanced kit.

kikkegek
Posts: 415
Joined: Thu Nov 17, 2011 2:12 pm
Location: Netherlands, The Hague

Re: Can I use the Bosch CNG injector for LPG?

Post by kikkegek »

hi C3H8,

sorry I completely missed your reply. Thanks for that. I have done some research in the mean time and found a couple applcations running the Bosch 2200 CNG injectors. Asked around a little and from what I found the Audi G-Tron and Dodge 2500 Ram are using them for CNG...but....the 4 cylinder Audi only makes 130hp and the 8 cylinder Dodge only makes 350hp on CNG.

so the Audi gets to 130/4 = ~33hp per injector
and the Dodge gets to 350/8 = 44hp per injector

and then I looked into the CNG system...these systems are run at 5-10 bar...so higher pressures compared to the LPG vapour that has a rail pressure of 2-3 bar. So at that lower pressure I'd guess they perform even worse?

I have contacted a dozen Bosch motorsport dealers and sent them an email asking for flow info on the CNG and if they are suitable for LPG. So far they only share gasoline info. Pretty weird for am injector that was developed for CNG operation/aapalication.

Why I am interested is because they would be an easy retrofit in a gasoline intake (direct fit) and because of their 9 Ohm resistance can be driven without peak&hold drivers directly of the Megasquirt or other aftermarket ECU. And they can be gotten in all kinds of sizes, with the 2200 being the biggest.
storage/project: 1974 GMC 25HUNDRED Suburban - fresh rebuild 350 small block - TH350-NP203 - 4.10 gears - IMPCO425 mixer
driver/project: 1977 GMC C15 Suburban - 454 big block - 4L80E- LPG VSI - 3.08 gears
sold: 1986 Chevrolet Suburban K20 Silverado

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