I filmed my 300CD after doing some IP tweaks. I still can't get much smoke if any... I'm wondering if I'm getting enough fuel?

• Stock 617.952 motor (~200k+ miles)
• 14psi MAX w/ wastegate fully tightened (w/ wastegate hose disconnected, 19-20psi MAX)
• ~1100F MAX temps on a LONG pull
• ALDA Removed
• Rack Limiter Removed
• Horizontal Throttle Stop turned in 1/2 turn
• EGR System Removed
• 4spd MT
• 2.47 Diff

Engine has been serviced: adjusted valves, corrected camshaft timing (was ~8 deg off), adjusted IP timing (24 deg), replaced both filters, cleaned tank screen and replaced air filter. I run on a mix of diesel and 5% B100.

Mercedes 300CD Exhaust - YouTube

have you checked your fuel pressure? connect a gauge right at the ip. The fuel pressure is controlled by the relief/return valve on the back side of the ip. Fuel returns to the filter housing and back to the tank. there is a ball and spring in the fitting. If the spring is weak your pressure will be low. 20 psi or better is good. Must get this right before doing anything more.

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1977 240D turbo

I mentioned your post to my wife, and her comment was why do you want to make smoke, as I am trying to not make smoke.

So, I am assuming that you think if it does not make smoke it must not be putting enough fuel in. If the goal is to make smoke then you are not putting enough fuel in. However if the goal is to make more power(I am reasonablily sure it is) then smoke is only an indicator that you have more then enough.

Are you making more power, and are you happy with the power level now? If so then be happy you are not making smoke. I still say you must check your fuel pressure, then if more power then you have now is the goal there are more things you can do.

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1977 240D turbo

X2. Smoke = unburned fuel = lost power. No smoke should be your goal, with improved power.

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Respectfully,
/s/
M. Dillon
'87 124.193 (300TD) "White Whale", ~392k miles, 3.5l IP fitted
'95 124.131 (E300) "Sapphire", 380k miles
'73 Balboa 20 "Sanctification"
Charleston SC

Well, I never checked the fuel pressure... but I did stretch the spring to XXmm per the FSM. My goal is not really to make smoke, but to make power. An indicator being that I have enough fuel would be smoke. Then I could dial the fuel to reduce smoke.


My concern is that others who have removed their ALDA and made similar adjustments get decent smoke (i.e. too much fuel). Whereas I didn't see much of a change in smoke. I still haven't messed with the max-speed or torque control governors in the IP.

Even though you stretched the spring I would still check fuel pressure. All mods past this point really do need good fuel pressure. It may well be fine but building on what could be low fuel pressure just is not a good idea.

I removed the alda on my 300d, no smoke either, turned out I only had 5 psi of fuel pressure.

Sorry if I sound a bit strident about this.

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1977 240D turbo

1/2 a turn is nothing. Give it at least 3 or 4 full turns, don't be shy it may require more than that if the Torque Control is set really soft, and make sure that the throttle lever actually is contacting the stop. Most of the cars I have tuned required a linkage adjustment to get full travel.

Make sure that after any linkage adjustment that the throttle lever contacts the vertical throttle stop, and that the manual stop lever actually stops the engine.

Is that 1100 degrees measured pre-turbo or post-turbo? In instrumented testing* I've seen a pretty consistent 200 degree difference under load. If that's post-turbo I'd say you should dial your fuel back a little. If it's pre-turbo you still have a little room to go before you risk melting your turbine wheel.

It's my understanding (I could be way off here) that the reason pulling trucks and drag race diesels smoke so much is that they intentionally run so much excess fuel that it cools the EGT's, sacrificing some power to keep the engine alive. I know top fuel dragsters do this. Of course, I would never advocate doing that on the street. Diesels still have an image problem in this country and major smoke shows, while pleasing to some of us, don't help with that image problem.

*400 or four and a quarter N-series Cummins in a cooling test I did at my old job.

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Whoever said there's nothing more expensive than a cheap Mercedes never had a cheap Jaguar.

83 300D Turbo with manual conversion, early W126 vented front rotors and H4 headlights 400,xxx miles
08 Suzuki GSX-R600 M4 Slip-on 22,xxx miles
88 Jaguar XJS V12 94,xxx miles. Work in progress.

Will do

I wanted to play it safe with the throttle stop... I haven't touched the TC, it was something I was going to do later. Yes, I ensured that the throttle lever did in fact touch the stop.

The measurement is pre-turbo... The theory of running rich to cool engine components is related to gasoline engines, not diesel where in inverse is true.

Well, finally got a chance to check my fuel supply pressure (after main filter, before IP):

Unclamped Return
Idle: ~13-16psi (unsteady reading)
3k RPM: ~20psi (steady reading)

Clamped Return
Idle: ~20psi (steady reading)
3k RPM: ~20psi (steady reading)

So it appears reasonable...