Increasing diesel engine power 2

[FZR1KG]

I've noticed that in hot weather I get less power out of my engine and also I get less power out of it when it warms up fully.
I'm guessing that this is because the intake air heats up so I have less air density.
My car has a turbo and an inter-cooler, more correctly an after-cooler.

I just thought I'd ask here if insulating the air intake lines in the engine bay before it enters the turbo would reduce the heat absorbed from the engine bay reducing the final intake temperature.
Would it be worth trying or is it a waste of effort?

 

[BrianPetersen]

The surface area of those pipes is insignificant compared to the surface area of the intercooler.

 

[tbuelna]

FZR1KG,

Actually, unless your diesel's charge air cooler is super efficient, the temperature of the air after passing through the cooler is still relatively high. Still much higher than ambient outside air temps, and probably not much different from underhood air temps. Plus, a large diameter tube makes a relatively poor heat exchanger.

In short, there is likely no appreciable amount of heat transfer occurring at the tube wall, and insulating it would not yield any real performance benefit.

You did not mention what make and model the diesel engine is. But if you're losing unusual amounts of power at warm/hot conditions, you might want to do a thorough check of the engine's sensors and fuel system.

Hope that helps.
Terry

 

[FZR1KG]

Its a 2002 Ford Courier (Mazda Bravo) with a 2.5L TD.

I wish the piping was short and cylindrical, its however various shapes and quite long inside the engine bay. Rough guess would be about 4 feet inside the engine bay and part of it is a pipe about an inch high and four wide with lots of bends to the air filter and back out to the after-cooler. The flat pipe is bent twice at 90Degrees across its narrow section and one 90degree bend in its wide section. There is nothing short and to the point in the intake plumbing.

The cooler itself is about 10x6 inches and located just in front of the radiator at the opposite diagonal to the air filter. Its about 2inches thick.

All up the plumbing from the air intake till the inlet manifold would be about 8 feet. Most inside the engine bay.

The surface area of the after cooler is quite small compared to the surface area of the plumbing in the engine bay prior to the turbo.

The engine is a basic Bosch VE type rotary pump, no electronic sensors other than a fast idle valve. It has a turbo boost actuator of a the same basic design as the standard VE pumps. Spring load and offset machined pin.

The only thing I can think of that could make the difference is the engine temperature or the air temperature of the air is being raised inside the engine bay prior to the turbo. Naturally the turbo adds even more temperature to this.

The fuel system is in good condition. This car has had this same characteristic since I bought it at 80,000km. Its on 240,000 now.

Every morning when its cold it has more pull. As the engine warms it loses power. On warm summer mornings it never has the same pull as a cold morning. Its not the fast idle as I run the car for five minutes before driving off but that doesn't affect the engine bay temp much at all.

The other symptom is when sitting at idle for extended periods its more sluggish till I get a km up the road or so. This is particularly bad in the summer heat such as days of 40DegC or so.

Needless to say the insulating would be an effort so I'm asking to avoid wasted effort.

 

[FZR1KG]

Clarification.
Its about 4 feet prior to the turbo and about the same after, making about 8 total. Though this is a very rough guess.

 

[patprimmer]

As others have suggested, it depends on the actual temperature differentials between the intake air charge in the air duct after the inter cooler and the air in the under bonnet area it runs through.

A simple experiment to measure the temperature of the charge and the temperature of the engine bay just adjacent to the air duct would tell you what for.

If there is a heat transfer to the charge air it most likely comes from the air duct passing close to an exhaust pipe. If so a VERY SMALL benefit may result from insulating both in that area.

Insulating exhaust manifolds can under some circumstances improve performance of turbocharged engines. Under other circumstances it can just open the waste gate wider.

Regards
Pat
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[FZR1KG]

"As others have suggested, it depends on the actual temperature differentials between the intake air charge in the air duct after the inter cooler and the air in the under bonnet area it runs through."

OK, I'm a bit confused here. The run from the inter-cooler to the inlet manifold is short. I saw no reason to insulate that.

However, I was under the impression that any temperature that that I drop before the turbo would be more significant as the turbo increases the pressure and the temp as a result linearly wrt boost pressure. In my case the boost is 15psi which I measured.

e.g. 20Deg change at the turbo inlet will constitute more than a 20Deg change at the outlet.

I may have to do some temperature checks at various points to find out whats going on. I just can't think of anything else that would cause the symptoms I'm seeing.

 

[patprimmer]

Look at the surface areas, look at the airflow and time for heat transfer, look at the temperature differences and make your own judgement on cost benefit.

I think the decrease in power from the increase in ambient is pretty much unavoidable.

If it is excessive, follow Terrys advice

Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers &

http://eng-tips.com/market.cfm

for site rules

 

[ivymike]

nobody mentioned it, but I suspect that a change in fuel density or a reduction in fuel delivery for another reason may be at play here.

if this is a direct-injected diesel, how important is having a little more or a little less air to net power output?

 

[Lou Scannon]

The loss of power could simply be due to an emission control strategy to maintain NOx levels at hot ambient conditions. (I'm aSSuming an electronically controlled, emissions compliant engine here).

 

[FZR1KG]

Its an indirect injection diesel, no fancy electronics at all. Very basic, no EGR or anything else. The closest thing is a PCV but I can't see how that would affect it to suit the observations.

I'll build up some temp sensors and measure the variation at different points while driving to find out whats going on.

Thanks for the help. I was hoping it would be something obvious I've missed.
Will post the solution when I work it out.

 

[SomptingGuy]

A 2.5L Turbochargged IDI fitted to a 2002 Ford? What engine is that (manufacturer, family name, link, etc)?

- Steve

 

[FZR1KG]

Its a rebadged Mazda Bravo.
The name is a Ford Courier. Mine is a twin cab ute (pickup).
IIRC in the US and Europe it was called the Ford Ranger but the US version didn't have a diesel option.

Later ones, 2003 IIRC went to direct injection so I have the a near last of the run of the old type. Not sure of the exact date of the change however.
The official designation for mine is a Ford Courier PE twin cab 4WD ute.

I'm posting from Australia so that may be where the confusion is. We get various mixes of different vehicles and with different names to elsewhere.

Links:

http://www.4wdaction.com.au/forum/forumdisplay.php?f=66

Its an Australian 4WD forum, I gave you a direct link to the Ford courier sub forum.
There is a thread there with pictures of peoples various vehicles.

Hope that helps.

 

[winfieldblue]

Your intercooler is probably a bit on the small side for a diesel engine of that size running that amount of boost.My 2.4 IDI toyota diesel runs 8-9 pounds of boost (no intercooler yet), and intake temps are around 100 deg.c on a cool day! Try to get a look at the size of the cooler on the BMW x5, small displacement turbo diesels generally need to shed more heat from the intake air than their petrol/turbo counterparts, and while petrol engines generally can cruise along the hyway with virtually no boost (and hence very little heating of the intake charge and intercooler), a lot of the smaller diesels run 4 to 8 p.s.i. at these speeds,requiring more heat to be shed even while driving at part throttle. Autospeed.com has an explanetary article on this subject.

 

[winfieldblue]

This article explains things much better than what I can:

http://autospeed.com.au/cms/A_109423/article.html

 

[LadaTrouble]

15psi on a Mazda 2.5 diesel? Someone has been fiddling with it,I doubt they put out more than 10psi standard.The blow off valve lets go at about 15psi.Where did you measure that? These early Japanese indirect injection engines had the breather feeding into the intake before the turbo....sometimes the intercooler gets clogged up with oil.If it has EGR the intake gets build up down stream too.

How is the smoke? Black,white,or none?

 

[FZR1KG]

Thanks for the link winnyblue.
I did actually know that which is one reason why I suspect that cooling the intake before the turbo would lower the outlet more effectively than cooling after the turbo.
The Courier intercooler is known for being a bit on the small side but it is mounted outside in a reasonably good airflow path when driving. Could however be better. May need to look into that too.

Ladatrouble,
The wastegate is stock, unmodified in any way. It was measured at the intake manifold using a T piece from the injector pumps turbo boost compensation system.
I have the manual for the car and the boost is average for this vehicle. The turbo works well from low rpm. Full boost is about 1700 RPM or so. It is on partial boost, about 10psi well before that however.

It is a garrett turbo factory fitted and they have a pretty good reputation here.

I've checked the oil in the lines from the PCV valve (no EGR on my model). Nothing to be concearned about and since the boost pressure was measured at the intake manifold and is within spec oil blockages shouldn't be a problem. Flushing the intercooler might be an option however.

My suspicion is still on too high a temperature going into the turbo. On a 45DegC day with a boost approx 1atm I figure the outlet temp should be just over double the inlet as it would pick some up from the turbo itself. Thats 90Deg+ assuming a cold engine. Alternatively it could be said that it would be similar on a cold day with a warm engine bay since the lines are long. Just how much it picks up I don't know.

Once I measure it up I'll have a better idea of what the temperatures are, all I can do right now is speculate.

 

[FZR1KG]

Oh, forgot to answer your question.
There is no smoke at all that I can notice.

 

[Lou Scannon]

"My suspicion is still on too high a temperature going into the turbo. On a 45DegC day with a boost approx 1atm I figure the outlet temp should be just over double the inlet as it would pick some up from the turbo itself."

There are scientific ways for estimating the compressor exit temperature fairly accurately.

 

[FZR1KG]

Like this one?

http://www.stealth316.com/2-turbotemp.htm

With my turbo data plugged in I get about 156DegC at the outlet of the turbo with no heat absorption of the ambient air while passing in the engine bay.

Probably already high enough to cause the effects I'm seeing. Add 4 feet of internal plumbing in an engine bay thats hot it can only get worse.

Thanks for the suggestion, looks like I need to raise the max temp of the sensors to measure it. I was planning to use 150DegC sensors, that would have failed!

May have to raise the intercooler to get more air flow and flush it just in case too.