ordering new cng trucks.

DT-12 is really Mercedes EPS (GS) transmission. It is not so new product, becouse EPS appeared in 80-s in 16 st variant and after long evolution they apdatet it to Actros MP3 truck with OM47x engines (DD11-13-15-16). As I know GS3 control unit works with Mercedes FR (ADM, VECI) unit only, so I'm not sure they can offer it with Cummins engine. But may be they made ataptation modul.... really not sure. Mercedes CNG engines are based on PLD engines, good with fuel economy, but IMO gutless.

400 HP ISX 12 got low torque but revs up easily like a car gas engine, so you feel it is not powerfull enought climbing hills only. Ok, lets sacrify something on altar of fuel economy and enviroment protection.

Many people ask why are CNG engines are so gutless? There are some reasons. First of all they use NG with 130 Octane ratio, it means that fuel burns slowly. There are easy ways to increase this process - advanced ignition and higher compression ore higher boost pressure. But it is not possible to change ignition advance charts becouse too early ignition = pinging and loosing power, too much boost pressure = too hot exaust, loosing MPG, exessive engine wear.

Other idea - to let engine run faster. And this idea is not good too. CNG engines for big rigs are made on base of diesel engines. Totally new engine would be too expencive and I'm sure at high output MPG will be really poor!

And any engine will not be efficient at so high speed becouse NG burns too slow, especially in big cylinders with long stroke.

 

There is very big gas engine made by ford, as I remember V10. This engine loose about 10% of HP ratio converted to CNG.

I converted my fourwheeler to LPG. Engine lost about 7% of power but runs much smoother with high octane fuel. I have additional ECM that injects LPG and use other ignition charts. I found that at over 3500 RPM there is no full combustion in cylinders and fuel keeps burning when exaust valve opens so I programmed LPG computer to switch to gas when engine revs up to 3500 rpm.

here many big gas engines are converted to CNG ore LPG. Many conversion shops mashine cylinder heads to increase compression ratio.

 

The company I contract 2 had 8 natural gas islg engines in Mack Granite concrete trucks. They were the best thing ever invented for an owner operator because they were always broken. I can't remember when all 8 were on the road at the same time and if it wasn't the trucks broken it was the filling station.

They had 6 speed Allison's and even they didn't help, they were slugs.

I can easily get about 15 loads out of the Allison trucks and up to 20 out of the eaton trucks with ISL's with 260L tanks, the CNG trucks struggled to get 4 loads and I'm not exaggerating. all the trucks are geared for 100km/h at 2000rpm.

They had 3 very large tanks behind the cab I'm not sure of the capacity but would have been over 300 liters each with a 50 L reserve that would give them about 20km range.

Another problem is no one could could fix them, sometimes they could sit at the workshop for a week until they could fly someone in to fix the problem I'm not sure how many techs over there are qualified to work on them.

Boral ended up giving them away, yes giving them just to get rid of them. The fleet manager told me it cost them over double to run them over diesel trucks.

A lot of bus companies over here are also converting there gas trucks back to diesel as well.

 

as I know Mack Granite are with Volvo D7 ore D11 engine and with Cummins ISM ore ISL, so sugest they have ISLG eninges, not ISX12G

 

The ISX12G has a different style of an aftertreatment system than what is found on diesels but it still has one.

 

I drive LPG engine every day.

We have Ford 4.0 V6 SOHC and Ford Essex 4.2 V6 running LPG.

Made for LPG ore Methan engine has 1:12 compression ratio becouse natural gas octane ratio is over 105

If you fit natural gas injection system on standard engine w/o cylinder head modificatio you have to avoid high RPM becouse mixture goes on burning in catalistic converter and it damages valves

That's why my LPG system injects petrol at high RPM to downgrade octane ratio to less than 95.

CNG and LNG engines cant start at below zero temperatures. Conversion engines starts on gas and switches to CNG in warming up phase.

That;s why CNG trucks for cold climate are equipped by coolant heaters like Webasto Thermo 90 ore Eber hydronic.