Turbos power question

[SasquatchSanta]

I installed a new stainless steel exhaust system, complete with muffler, last year and it completely eliminated the whine of the c-turbo.

One of this summer's projects is to add a cross-over pipe and a second stack. When I order the raw material for the twin stack project I'm seriously considering getting rid of the new muffler and going to dual straight pipes. I'll probably regret it the first time I go on a long road trip BUT I miss the thistle.

I'm also wondering what the odds are of the twin straight pipes having a positive effect on my fuel mileage and overall performance (power).

 

[jimk]

Thanks Jason. ERROR was between keyboard and chair.


So 2.5"/2=1.25"x1.25"x3.14=~4.9sq inch x 15psi=73.5lbs.A lot less than the 117 I stated - but still a factor. I'll skip the stem as the valve size is a guess.

Ken,
I might have to [respectfully] disagree with fuel efficiency being #1. For engines (all things being equal) it does improve fuel efficiency by reducing pumping losses. It may allow an engine do the same work at a lower engine speed, or allow a designer use smaller(thus lighter)engine...It's a benefit but the latter two don't apply here. I'd think If someone wanted to improve fuel economy they have come up with a diff gearset for the trans or transfer case.I wish they had.

TM 9-2320-361-10 page 1-18 reads:
Fuel consumption*
-LD-465-1/1C---- 5 - 6mpg
-LDT-465-1D---- 5.15 - 6.18mpg
*based on diesel fuel and 1500rpm

I read (somewhere here) the LDT's turbo was a solution for the smoke issue. Some gov agency(EPA?) granted the manufacturer a waiver to build additional vehicles if they were cleaned up. I think that post said a subsequent production run was denied. That may have signaled the end of the M35 series (and at a time when emissions became a major concern ~ after 1970). Smoke would be my #1 "as designed".

Most turbos are used for more power. My #1 "in general". The LDS turbo seem all about power. My commercial Mack as almost undrivable when the compressor's t-bolt clamp breaks (a common problem(3x)/ might manage 30MPH w/oT). Turbos get more O2 in the chamber. Power comes if there is available fuel. More efficient?Yes. More fuel used?Yes.

The manifold may act as a aftercooler but it's efficiency would drop to 0% as the water temp reaches the charge temp. Maybe a super high boost would benefit some. Even if the manifold is colder there is not a lot of surface area inside. Efficiency would be extremely poor. I took a quick look for a sample compressor discharge temp(HP - Turbochargers). I'll give just the results -247*F (15psi/ 300cid/ 350HP/ 80*amb/ 70% comp eff).

Text states:
"If jacket water is used as the cooling media,at 180*F the temp drop will be (250-180) x .7=49*F . This results in a charge air temp of 210*F. The small decrease makes it impractical unless the compressor discharge temp is at least 300*F."

Note: this example is a water to air intercooler with 70% eff. rating, not an intake manifold housing, running 15psi boost, and only 180*F coolant.

That LDS wastegate is a big player. Wastegates allow[a different] turbo to run in the most efficient part of the compressor map. The turbo may create more boost at lower RPM and protect against excessive turbine speed and overboost . Less compromises.

JWaller,
25psi? A LDT turbo might help.
An intercooler too.
Last night I tried to think up a good location for one. Still thinking.JimK

 

[jimk]

what is the deal/reason for the double vanes on the impellers? also, why do some blades have them and some not (as in the D turbo image)?

Curve can be thought of as an axial compressor for the basiclly radial design. It reduces shock loads at tips and helps air move into the turbo. Some are shorter(d) because more would reduce airflow( the curved aspect is starting to to close opening).
Note- much of radial aspect is hidden from view.
Here is a head-on view of the D.

 

[Westech]

All this talk about inlet temps. I run mine after the turbo half way in the little elbow pipe, and I run mine up to 1000* and will run it constant at 900* with out any problems in the past 3 years now. I have no idea how hot it is going in to the turbo but would not think I'm dropping too much EGT's there is alot of air flow in the exhaust.

 

[jimk]

I wrote:

Curve can be thought of as an axial compressor for the basically radial design. It reduces shock loads at tips and helps air move into the turbo.

I've been thinking about this and have some mixed feelings. I'm not an engineer so comments/ criticism welcomed.

A curved tip used to be called the 'inducer' the thought was, as I stated, a pumping aid. It may indeed work that way at low speeds. The problem I'm having is that a radial compressor's output is very progressive. Air flow increases greatly, generally the sq. of the speed. Axial flow compressors air flow increases are linear (or maybe tiny bit progressive depending on whether the blade is airfoil in profile). There is a conflict having both these on the same fixed impeller. I'm beginning to think the curve is just a COMPROMISE so as to allow the most air flow during a specific operating range. The curve must hurt airflow somewhere(above/below). In probably has a lot to do determining the shape of the compressor map.

I now feel that it is more for the "reducing shock loads' stated. Being at the correct angle [at certain impeller speeds] allows air to enter the turbo more smoothly (air-moving forward into a rotating wheel) and -before- going to the part of the pump that is doing most of the work.

The D impeller looks to be a progressive spiral. The design may just reflect all 'issues' as the air moves thru the pump. JimK