×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Increasing diesel engine power
2

Increasing diesel engine power

Increasing diesel engine power

(OP)
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?

RE: Increasing diesel engine power

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

RE: Increasing diesel engine power

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

RE: Increasing diesel engine power

(OP)
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.




 

RE: Increasing diesel engine power

(OP)
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.

RE: Increasing diesel engine power

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
See FAQ731-376: Eng-Tips.com Forum Policies for tips on use of eng-tips by professional engineers &
http://eng-tips.com/market.cfm
for site rules
 

RE: Increasing diesel engine power

(OP)
"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.
 

RE: Increasing diesel engine power

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: Eng-Tips.com Forum Policies for tips on use of eng-tips by professional engineers &
http://eng-tips.com/market.cfm
for site rules
 

RE: Increasing diesel engine power

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?  

 

RE: Increasing diesel engine power

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).

RE: Increasing diesel engine power

(OP)
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.

RE: Increasing diesel engine power

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

- Steve

RE: Increasing diesel engine power

(OP)
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.

 

RE: Increasing diesel engine power

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.    

RE: Increasing diesel engine power

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?

RE: Increasing diesel engine power

(OP)
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.

 

RE: Increasing diesel engine power

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

RE: Increasing diesel engine power

"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.

RE: Increasing diesel engine power

(OP)
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.
 

RE: Increasing diesel engine power

No smoke on an indirect injection diesel? Get someone to confirm that from the rear as you are under full noise.It may be under fueling,which will explain the power loss.These things are pretty dirty and should have a little black smoke under load.I'm in NZ and pretty familiar with small Japanese diesels...we have a Courier at work that has done 1,450,000km,and still won't lie down.It's very gutless of course,a joke in the company considering we are a Mitsi dealer.

RE: Increasing diesel engine power

(OP)
Will try to do that this weekend. We're having guests over so I'll see if he minds following me.
Good to see the reputation of the courier engine is going strong, 1M45 km, thats some mileage!

I don't understand why there would be power loss as it warms up if it was under fueled. Shouldn't it be the same low power all the time?

BTW, my mate has a Triton dual cab diesel. My courier is faster than his and his is a later model, not sure what thats all about LOL

RE: Increasing diesel engine power

The "fast idle valve" might be retarding the start of injection if it's the same set-up as the toyota rotary pump which has the engines coolant running through the sensor. I disconnected mine, and then burnt out a set of glow plugs every month, melting the tips off them! Retarding the injection timing fixed this problem.

RE: Increasing diesel engine power

Yeah,you have to use a 10mm spacer jammed into the coldstart when setting the timing on those engines.But his 02 courier should have an electronic pump,so no cold start valve.

RE: Increasing diesel engine power

I think you would be surprised to find that your intercooler CORE temp varies almost exactly as the performace does.  

If you say you can sit and idle for 5 mins and still have performance for a short distance, why wouldn't the pre-compressor intake pipes already be up to engine bay temps?  If the intercooler is far enough away from main engine bay heat soak (at the front of the car) then it will not heat up until the first time you compress the air.  If it is small in size, or poorly positioned in the airflow, the core may never get back to the ambient temp in normal driving, acting as a heat soak, controlling temps below a certain level but also not allowing minimum temps to be reached again.  

Have you got a cheap multi-meter with a k-type probe?  Epoxy the sensor to the IC core, tape the meter to your windscreen and have a drive.  Also check your intake piping temps between the compressor and IC, you will see that they will return to closer to ambient temps alot quicker.

A larger or more efficient intercooler is the answer.

RE: Increasing diesel engine power

FZR1KG, I don't mean to be pedantic but your rule of thumb of the temperature doubling is based on a common but very serious error that needs to be quashed. It can only apply if you are using an absolute temperature scale and then the factor would need to be adjusted to something like 1.1. For example, if the outside air temperature is 0C or -5C what will the boosted air temperature be by your rule?  

RE: Increasing diesel engine power

(OP)
Compositepro,
No worries. I don't think you're being pedantic. More that I wasn't clear in what I wrote. It wasn't a doubling of the temp in DegC I was using to get that figure, I found that error earlier when I forgot to convert to Kelvin in my quick spreadsheet to get me a rough idea and entered a neg temp to work out what I was seeing in the early winter mornings. It got colder as a result of being compressed! LOL

70btdc,
You have a very valid point.
That would also explain the effects I'm seeing.
I'll flush the intercooler and raise it up so its more into the air flow and see what happens.
I no longer have a multimeter with a thermo couple input. I had a great data logging multimeter till I lent the thing to a co-worker. Now I have a fancy paper weight.

Just curious, how would I calculate the required size of the intercooler for this car. Its a 2.5 litre turbo with about 15psi boost. Produces about 90kW of power if that is a factor.
While its not blocked due to oil from the PCV, how much would a film of oil in the intercooler affect its efficiency?




 

RE: Increasing diesel engine power

methanol or water injection.

RE: Increasing diesel engine power

As a heat transfer engineer by day (job), I would say that unless you are interested in calculating to the third decimal place, the heat transfer through your tubing walls is negligable.  The only help you will get by doing that would be your feelings.  I work with an intercooled gas turbine and we would LOVE to get some credit for the heat lost by the tubing walls pre intercooler but sorry, we have to do it with lots and lots of (expensive) heat transfer surface area in the intercooler.  And, yes, our Brayton cycle machine suffers when the temperatures get up to summer time levels.  Enough that there is a measurable difference between early  morning and mid (Hot) afternoons.

The post about the potential underfueling condition caught my eye.  Otherwise, I think you are just dealing with the ravages of the PV=nRT law.  Hotter air has larger volume and it affects turbo performance, tube wall friction, after cooler efficiency and effectiveness, fuel properties, etc.

I drove a turbocharged IDI diesel for years and I can't say that I ever noticed any difference hot to cold, but then again, my turbo may have had as much shaft horsepower as your little 4 banger.  (See tongue in cheek.)  But that said, mine was way over fueled, and if anything I had problems in the other direction due to that.

Typically a turbo will spool up and overcome lots of the detrimental effects of hotter air, but if you are underfueled, you will never push your turbo hard enough to spool it up to make a difference.

Remember too that at a hotter starting point, the turbo exit temp is hotter and hotter air has a higher volume which causes increased pressure drop through your after cooler.  It is all working against you.

Go for checking the fuel system.  I think that is where you will get the biggest bang for your buck (quid).  Changed your filters lately?

rmw

RE: Increasing diesel engine power

(OP)
Well, its seems like its a case of mainly under fueling.
A quick adjustment to the fuel delivery made a world of difference.
I say mainly because it still has the same symptoms but much milder.
Before it would get quite sluggish, now its just a slight power drop. Its noticeable if looking for it but otherwise it drives like it should.
I'm happy with the results. When summer hits I'll see if it makes any more change to the performance but right now its going fine.

Thanks for the advice everyone.
 

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources