3 Turbo Questions

[Guest Anonymous]

There are 3 things I've always wanted to know about turbos and i think u guys might be able to help.

 

1. After a turbo settup has been installed, can a larger or different trubo be freely or relitively easy to swap in?

 

2. Does the turbine produce any backpressure?

 

3. Is the acceleration the same durring the time before turbo lag has been overcome as the acceleration with the same engine with no turbo installed? Like two identical cars except one with a turbo and they take off at the same time. Will they be right next to eachother untill the turbo kicks in on the one car? Or is it the backpresure of that turbo (if there is backpreasure) keeping the engine from fully breating?

[scottyMIz]

I can answer alittle depending on the system you should be able to change turbos fairly easy some mods are required for bigger turbos.The turbo does produce back pressure it's just like a muffler if you run a turbo car w/o a muffler and a n/a car w/o a muffler the n/a car will be alot louder.As far as the two cars side by side i don't know for sure but my lag is almost not noticable.The turbo engine has lower compression so that would hurt it during lag.If i rev up my n/a z it tachs up quickly if i tach up my turbo it tachs up slower cuz it has to go thru the turbo.But if i step on it in first in both cars you know which one will be quicker.Hope it helps and i didn't steer you in the wrong direction.If i'm wrong guys point it out so i can learn from it too.

[Guest Anonymous]

I don't know either and would like to. I am considering a low cost turbo kit for the 355 chevy. At least I think it is low cost. The guy wants $900 for everything including both headers and it is a draw through so there are no electronic timers and crap to worry about. just a wastegate, the air pipe plumbing, the oil lines, and down pipe. Looks very simple and clean.

 

Any opinions?

[Guest Anonymous]

I got another question. Why are intercoolers left unpainted? Wouldnt it be better if they were painted black like a radiator? I remember something about black being better at absorbing heat and stuff and thats why they paint radiators black.

[SleeperZ]

If you wanted the IC to absorb more heat, it should be painted on the inside

On the outside, you don't want it to absorb heat, you want it to reject heat, avoid heat-soaking it.

 

As far as I know, the only turbo that bolts up to the L28ET is the T3 turbine housing. A hybrid T3/TO4 will bolt to the exhaust, but the intake needs to be modified to accomodate a larger compressor.

 

The turbo does build backpressure, and how much depends on the A/R of the housing. The bigger the A/R, the lower the backpressure, but the lag increases. A larger A/R will produce more top-end power at the expense of throttle response.

[Guest Tom Scala]

Painting a radiator or IC with a light coat of flat black will help it transfer heat better not absorb it. Alot of factory ICs and just about all radiators are painted and I'm planning on doing that to mine. Polishing a radiator or IC makes it look pretty but reduces it's efficiency and it's ability to transfer heat to the atmosphere. The difference may not be great but it's real.

[Modern Motorsports Ltd]

quote:

---

Originally posted by SleeperZ:

If you wanted the IC to absorb more heat, it should be painted on the inside

On the outside, you don't want it to absorb heat, you want it to reject heat, avoid heat-soaking it.

---

 

On a rad it enhances heat flow out of the radiator and is this not desirable on an IC as well? Unless your IC is in the actual engine bay I can't see heatsoaking to above ambient temp ignoring the internal flow.(black flow it in as preferably as out? ie. same advantage regardless of direction of heat flow?)

 

Ross (skipped the thermo courses) C

[pparaska]

The major mode of heat transfer inside and outside of a radiator and IC to the surroundings is through convection. Radiation has a back seat, but is not insignificant. Radiation is all about the emissivity of the surface (polished AL being low emissive) and area. The product of these governs radiant heat transfer, as well as the properties of air and temperature differences.

 

Worry about getting more presented area and air flow to present to the IC first, as well as an sufficiently large volume and efficient internal design and good conduction between the fins and tubes, then worry about radiant transfer later.

[clint78z]

Yes heat transfer with low pressure drop is the key. This issue is sometimes forgotten as well. Think of an intercooler as a heat sink, you pin it for 10 sec and turbo heats the air. The temp of the metal is around ambient and the air warms the metal up. If you have a big intercooler with lots of metal it will not heat up as fast and therfore keep air temp lower.

 

Lesson big is good in general, there are other little tricks to make it work better.

[BLKMGK]

Clint is exactly right. I read a very interesting article written by a group that was trying to make a sprayer for their intercoolers. Come to find out that spraying water on an IC as the turbo went into boost made NO difference in inlet temps! There was simply too much hysterysis (sp?) for it to be effective. They figured out that if they sprayed the intercooler a bit BEFORE going into a period of boost that it made a difference. I don't recall what they finally figured out but I'll bet controlling it all was "fun".

 

Local shop just picked up an acocunt with Nitrous Express. Thumbing through their catalog I ran across an "interesting" piece - a spraybar for NOS designed to spray an intercooler to ide it before a run! Seems kind of expensive to me, they may order one to try on the dyno just for grins though

[Mike C]

The Mitsubishi T04 and T05 should bolt up to the Z manifold as well. I have a ZX turbo manifold and a T04 and they bolt up. Appears to be same pattern/size as the T05 on my friends Typhoon. Mitsubishis have watercooled center sections as well for better durability, but the T04 is smaller than the stock T3.

[Guest Tim78zt]

on the subject of painting your IC, or aluminum radiator for that matter, I asked the local Greddy dealer ( Brice at Alamo Autosport) if I should paint my IC and he said only if I wanted to destroy the efficiency. That was the end of that conversation.

 

Tim78zt

[BLKMGK]

My understanding is that paint ends up acting as an insulator. However there are some paints made for this application so perhaps that woud work better. I've heard so many different points of views and opinions on the subject that I just generally leave them alone - both radiators and intercoolers. If it comes painted I leave it that way, otherwise I leave it bare

[Guest Tom Scala]

That salesman needs to take a couple of Thermo & Heat Transfer classes.