Does the 1972 4.5 require a constant exhaust backpressure to run properly? Is there a relationship to the vacume system and backpressure?

Tobst:

Backpressure from the exhaust is take into consideration when setting the valve overlap (the amount of time in degrees where the intake and the exhaust are open at the same time). This helps to purge the exhaust out of the cylinder and also to draw extra charge in from the intake.

Vacuum and exhaust pressure are definitely related -- if you have excess backpressure, you will have low vac.

One quick way to tell is to hook up a vac gauge and start the engine. If the vac starts out around 17" (as it should) and gradually falls off, getting lower the longer you idle the engine, you have an exhaust restriction. Good way to check for clogged cats (not a problem in your case).

Are you still chasing poor performance problems?

Peter

__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

Yes, car ran well but ran hot with NEW system, starting to run ruff now will have the tech look at it monday. Crap! Just don't understand whats up such a nice car not to enjoy. Thanks for hyour intrest.

Tobst:

Something is definitely wrong here, I've heard that several other folk have used TimeValve with excellent results.

Check the vac, you may have something strange going on. I cannot imagine what, but there has to be something.

I suppose you could try running it with the muffler off, just the header pipes, but it will be LOUD!

The only other thing I can think of is a fuel mixture problem. Have you investigated that?

Peter

__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

Yes Peter, and that was one reason I chose Timevalve. It is clear to me they did not build the correct system for my car. That being said I have not checked the air/gas mixture because it was never a problem before. I think something happend when I drove the car with the Timevalve. There was so much backpressure it affected the _________and now I am having this problem. Just having to check everthing.

Its a weird thing - overheating an engine - can remember when 220Sb of mine overheated then always ran hotter than normal forever after.... even after i recored the radiator, replaced water pump, etc.

Tosbt, sounds like you are royally pissed off with Timevalve - and i dont blame you. Stainless pipes are controversial item that even diesel truckers are skeptical of....... on account of how they can effect engine performance. More than just back pressure they add heat too - especially if you run stainless all the way to exhaust manifold.

With lawyers, service records and affidavits from your mechanics you might be able to go after Timevalve Corp. located in Connecticut - suing and settling for new engine that MB can provide for $8-12G. Hell, you might even get punitive damages too...... assuming you arent the first to file complaint against Timevalve.

Basically, if stainless pipes are good for engines - how come auto manufacturers or muffler shops dont use them? It seems kinda flakey that Timevalve calls their pipes "OEM spec" as if MB endorses their product.

As I've said earlier, when looking into stainless pipes for my 280/8 practically every motorhead and pro mechanic, including my pal at MB dealership who gave me parts at contractor rates, advized against it.

OEM pipes/mufflers for MB are a low corrosion steel with some "stainless" properties. They are also considerably thicker that typical stainless steel pipes, so transfer heat less efficiently.

I still don't understand the physics of how a pipe that transfers a little less heat out (and it's only a little less, mind you, and the pipes are generally thinner to boot, so the effect is even less!) can have ANY effect on the passage of a gas through a large diameter tube!

Back pressure is a function of flow resistance, and believe me, a muffler is going to produce LOTS more backpressure than the temperature effect. Even a resonator will have more effect.

Before I believe that stainless steel pipes have any measureable effect on back pressure, someone is going to have to show me some real temperature/pressure data, not "backyard engineering" gossip.

A pipe is a pipe -- gas flow is going to be related to temp and resistance ONLY, not the composition of the pipe.

Peter

__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

I can not make a qualified comment on stainless pipes itself, what I can say is the system that timevalve built for my car was not to OEM specks. When I talked to Dave and Scott at timevalve I was told that this was the system they used for the 450SL and SEL "all the time" and that the engines were the same and it should work on my car". My last e-mail from Dave was in effect that I did not know what I was talking about (I admit I do not make muflers or know much about them) but when I pointed out that the picture of the 300SEL 4.5 on his web site was the same one as in the service OEM service manuel and that is not what he sold me, he never replied to me again. Do I think the timevalve system damaged my engine? Yes I do.

Well, I COULD see how it could possibly affect it. Thin stainless would give off heat more than thick inefficient OEM steel. Therefore, due to the heat loss, pressure in the pipes would decrease (PV=nRT, if T decreases and the # of gas molecules stays the same, and as R is a constant, P and V go down, or think of P1V1/T1 = P2V2/T2), therefore causing LESS backpressure on the engine. Of course, that's only my THEORY and what I THINK MIGHT happen That, of course would NOT damage the engine.

However, if there was too much backpressure (IE: from the wrong muffler), that WOULD cause damage... especially to the head gaskets I would imagine... and other things (possible exhaust gas would exit via the intake when valves first open, possibly leading to burned INTAKE valves over time, as well as burnt exhaust valves due to the pressure...)

__________________
Current:
2021 Charger Scat Pack Widebody "Sinabee"
2018 Durango R/T

Previous:
1972 280SE 4.5
2014 Jeep Grand Cherokee Limited "Hefe", 1992 Jeep Cherokee Laredo "Jeepy", 2006 Charger R/T "Hemi"
1999 Chrysler 300M - RIP @ 221k

Its reflection of heat upon internal chambers that I'm thinkin would boost back pressure tremendously....... kinda like stainless shield under stove burners increases intensity of flame.

Thicker low nickel content steel pipes would logically absorb much more heat than would stainless steel..... same as chunky cast iron frying pan, robbing heat from the flame, will burn less food than thin stainless pan on the same burner at the same setting.

Since stainless pipes are notorious for reflecting heat outward, we've gotta ask ourselves how much heat they radiate inward as well. With stainless getting hotter and hotter on the outside it does not mean internal passages are any cooler - in fact the opposite might be true.

Those *******s at Timevalve in Connecticut rust belt where road salt dissolves undercarriages probably know they are selling risky aftermarket products not designed for Texas climate...... Hell yes, I would file complaint with consumer agency in their home state. http://www.state.ct.us/dcp/

I think we are miss-communicating here.

Stainless steel exhausts are usually VERY much thinner, since they don't corrode very much, so they are much lighter and let the heat OUT of the exhaust gas faster.

This is a problem with headers, as the heat can cause problems right up next to the engine. TimeValve exhausts don't include a replacement for the cast iron manifold, so that isn't an issue here.

Tobst had a back pressure problem. This is a completely different subject that heat dissipation. Stainless steel exhausts don't "reflect" heat anywhere, it simply penetrates the thinner material and leaves faster. This heats up everything around the exhaust a bit more than regular steel pipe would, but there is absolutely NO extra heat generated, reflected, refracted, or bent around a corner. Less heat INSIDE the pipe gives less back pressure, not more.

Don't mean to be a smartypants, but physics is physics. Rumors, third hand experiences, and "them stainless pipes burned up my motor" type stories just muddy the water!

Finally, tosbt may have a coindicadental problem that appeared at the same time as the installation of the exhaust. He did experience poor performance, a sign of excessive back pressure.

I don't believe that excessive back pressure will damage an engine much -- no charge can get into the cylinder to burn, hence the low performance. No way that will lead to burned valves, etc, Will carbon it up pretty well, but that is another issue.

Peter

__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

The original owner of my 250SE installed a stainless steel exaust system before I got it. Hasn't posed any problems for me

This is the first time I've heard anybody say stainless pipes provide cooler exhaust flow and produce less back pressure.

If you are saying pipes that get hotter than hell are cooler on their inside passages, then I gotta be worried about my stock exhaust system because it never gets hot at all.

Since after-market stainless pipes are notorious for getting hotter than steel, it strikes me they retain more heat than do their stock counterparts. This seems obvious to me.

Reminds me of cast alloy engine casing at BMW motorcycle shop that somebody had polished to shine like glass..... gone were heat dissipation properties and the casing itself would steam when spat upon.

Take a perfectelly running car and put a new exhause system on it, find it beheaving like the timing is off and/or is flooding. Run the car to "smooth it out" for about 30 miles, watch it near red line as you make it back to the tech. Replace the new exhause system, runs fine no backpressure but allways runs hot. All I know is that I could see but now I'm blind.

Diesel: Yes, pipes that get hot as hell on the outside are MUCH cooler inside. Why, you may ask? Well, think of it this way: If you have 2 hot water pipes of equal length (let's say 100 feet) and equal composition (say copper) outside in a cold (let's say 0C) environment, and put insulation around one, the outside (where you touch the insulation) will be cold, yet the inside will retain hot water. The other pipe, however, will feel hot outside, but the water coming out of it will be much colder. The pipe with insulation is similar to a thick steel exhaust pipe, the one without it is similar to a stainless pipe.

Heat is energy. The hotter pipe is absorbing the energy FROM the exhaust gas INTO the pipe material, which in turn is radiated to the surrounding air/environment. While the pipe ITSELF may feel hotter due to this, the air inside is COOLER than it would be inside a pipe with poorer heat-transfer abilities. The heat is LOST to the pipe. The pipe isn't heating the gas, remember, the gas is heating the pipe! If the gas is heating the pipe, it therefore must be LOSING more heat than if it weren't. Think back to the insulated vs non-insulated pipes: the non-insulated one FELT hotter because the water was heating the pipe. The water coming out however was COLDER because it LOST energy in its efforts to heat the pipe (and indirectly, the outside air as well).

Therefore, going back to PV=nRT, the pressure inside the stainless pipe would be less.

Also, heat does not "reflect" off of surfaces. This is a VERY common misconception! Light reflects, and the material often reflects it back onto itself before reflecting it off, so a shiny tool in the sun would feel hotter. However, if you had 2 stainless pipes, one painted black inside (let's asume the paint has NO insulatory capabilities) and the other "shiny" inside, there will be NO difference in convection inside the pipe. Convection is commonly misunderstood: It doesnt happen due to "heat reflecting" it happens due to the fact that the heat will be lost on gasses closest to the outside of the pipe, while the gasses inside remain hot. The hotter gas will then simply diffuse to the outside and the cooler gas diffuse to the inside (convection is nothing more than diffusion that you can often see!). This doesn't affect flow qualities of the pipe negatively, in fact, it may create a vortex (very small scale) which would HELP the gas escape quicker!

Believe me, if you tried suing over this, they'd hire physics experts who would say stuff similar to this, use so many tests and theories, etc, you wouldn't stand a chance. Sorry to say, but the stainless itself is not to blame. However, excess backpressure due to a SMALL MUFFLER may be!

Excess backpressure:
1) Prevents all exhaust gas from escaping a cylinder, leaving more heat inside it!
2) some of this exhaust gas can escape into the intake manifold when the intake valve is first opened, not only heating the intake valve excessively, but changing manifold pressure!
3) Carbon buildup due to incomplete combustion because old exhaust gas doesnt have enough O2 to burn fuel!
4) Higher pressure inside cylinders due to exhaust gas not exhausting, possibly causing head gasket issues!

Remember, intake and exhaust valves are built differently. Intake valves aren't meant to withstand nearly as much heat as exhaust valves! Plus the excess pressure, etc... I'd first check head gaskets if I were you, tosbt. It's POSSIBLE that you have a minor (or major ) crossfiring condition between cyls, often BECAUSE of extreme overheating (you said it overheated, this fatigues head gaskets!)

__________________
Current:
2021 Charger Scat Pack Widebody "Sinabee"
2018 Durango R/T

Previous:
1972 280SE 4.5
2014 Jeep Grand Cherokee Limited "Hefe", 1992 Jeep Cherokee Laredo "Jeepy", 2006 Charger R/T "Hemi"
1999 Chrysler 300M - RIP @ 221k