[GrumpySteelMan]

Ok I got a little bit more work done on teh plumbing of the turbos and now have them clocked.

After looking at your plumbing, I think you should rethink your routing. I didn't realize you were running your downpipes between the radiator and engine, I thought those were your pipes from the manifolds.

That pipe running by the coils on the passenger side will probably melt them. You have to realize that EGTs between the head and turbo get up to 1200-1400 degrees F, but after the turbo can be 300 degrees lower.

Let me grind my mind and figure out something

 

[Telion]

hmm, the pipes that exit to the exhaust pipe are not in the pic yet they will take an immediate right angle right angle off the turbo and get wrapped over the passenger side axle and back out. The pipe you see that is going across the top of the engine is alos getting wrapped and has about a1/4 in clearance on each side. Let me know your continued conerns. I do have the ability to still run it wrapped around the drivers side axle. I still have time, your suggestions and ideas is what this thread is all about, next documenting things as I go.

***current sidenote I did forget to mention that the turbos won't literally be sitting on teh radiator as in the pics the goal will be to get them two inches off it.***

Relocating the pipe across the valve cover would be ideal though since that space may get used at a later time.

 

[Telion]

Its looking really clean. Very impressive. Where are you gonna put the p/s res?

Is the hood going to rub the blue coupler at the back or is there just barely enough room?

Sorry I noticed that I didnt answer your questions. there is plenty of clearance where the elbow coupler is in the back just doesn't look that way in the pic.

I have not decided on the power steering reservoir yet I want it some where that is still easy to get to and being aluminum I guess it would be nice to keep it somewhat visible.

 

[Dv8]

Looks good sitting there, but I don't see that setup being very efficient or practical. A twin is a task in of itself, thats why I went single. (Yes I let some info out.) I want higher hp and I'm no daily driver; which doesn't mean a single wont work for the average manual trans 3.2.

That plumbing is out of control and it looks like at least one turbos oil drain is pointing up instead of down??

Please don't take my criticism as anything short of constructive.

~Dv8

 

[Forevralegend]

if i were you id do away with that other turbo on the driver side, simple is better. Unless your going twin turbo just to say you have a TT. Just stick with a bigger single turbo, there are plenty of turbos out there that spool quickly and have good range. Other than that, great work.

 

[GrumpySteelMan]

I would probably suggest running the twins low behind the radiator with each header feeding into each turbo through a u, then a straight pipe, then a 90 degree. Each turbine inlet facing downward, with each turbine outlet facing the center, so they could immediately y-in together. This would also be easier to make stable and reinforce the piping mounts, as hanging turbos off long hot pipes isn't always a winner.

This would keep all that freakin heat out of the top of your engine bay for sure, compared to your current setup. Seriously, the pipe(s) running up the firewall will also heat the passenger cabin.

I don't know how I didn't see this coming. Should have asked.

I'd clock the compressors to place their outlets perpendicular to the ground facing upward. Then turn them outboard and to each side of the IC.

This scheme would put the inlets facing outwards and keep all the exhaust heat low and central where the greatest airflow is available to carry heat away from the upper engine's sensitive parts. It would improve efficiency by being a shorter piping run as well.

This is the best case scenario IMHO. You can probably get away with what you're thinking, but you also need to think about the brakes being right next to the hot pipe...brake fluid boils.

 

[Telion]

Looks good sitting there, but I don't see that setup being very efficient or practical. A twin is a task in of itself, thats why I went single. (Yes I let some info out.) I want higher hp and I'm no daily driver; which doesn't mean a single wont work for the average manual trans 3.2.

That plumbing is out of control and it looks like at least one turbos oil drain is pointing up instead of down??

Please don't take my criticism as anything short of constructive.

~Dv8

Forevra I am going to reply to both in one if that is ok, yeah part of the reason is to say that it is a TT and I am going to head the warning of running the pipe across the valve cover. the end intent is to take the #%)z manifolds and flip them forward but that is going to require another enigine pull and I would like to get atleast a few tt runs down the track this year without having to pull the engine . . .hmm I could put the PS on my mock up engine and see if I can swing them forward and around these units. Thank you for posting each of you. Your constructive criticsm shows that you care(<couldn't think of a better word)

 

[Dv8]

Forevra I am going to reply to both in one if that is ok, yeah part of the reason is to say that it is a TT

A guy says I have a Twin turbo Legend, another guy says I have a Turbo Legend; first I praise both of them, but the next logical question is which one is currently running and what sort of power are they making.
To me twin or single, 5 or 6 spd, it makes no difference. If I could get my hands on a young 5spd trans under 40-50k, Id give them my 6spd trans.

Besides, I'll always say my Legends boosted, not turbo'ed..'cause it sounds better.....

~Dv8

 

[GrumpySteelMan]

I prefer 'blown'

All iterations.

 

[Antares]

I prefer 'blown'

All iterations.

^ sig worthy

 

[Telion]

sorry I have been MIA for a while my laptop crashed and I am at the point where I am pretty sure I need a new hard drive for it but I have the passenger side header finally positioned to be welded need to get a few mild steel elbows thow. If anyone has leads or contacts for these I could use it. I will get a pic when I load the digital camera driver to my wifes computer. as for the drivers side that #$%$%^ is a tighter space than the passenger side I almost said #$%%$# it but then when I was under the car (where the AC pump was looking up toward the header on the drivers side to my surprise there was a good deal of space. So I am now contemplating mounting that turbo where the AC was and seeing if I can get a custom weldup job don that will route the header at an angle down to it. Can't touch the exhaust yet because I am still waiting on a 3" high flow barrel spun cat and the flex pipe but the Y and the muffler came in and the muffler was bigger than it looked in the pic . . .dayum but the welds are great and it looks to be built well. on that note I also found this that seemed to be good knowlege, it also touches on the misconception and clarification of backpressure (I fell into this category)

The following excerpts are from Jay Kavanaugh, a turbosystems engineer at Garret, responding to a thread on http://www.impreza.net regarding exhaust design and exhaust theory:

"Howdy,

This thread was brought to my attention by a friend of mine in hopes of shedding some light on the issue of exhaust size selection for turbocharged vehicles. Most of the facts have been covered already. FWIW I'm an turbocharger development engineer for Garrett Engine Boosting Systems.

N/A cars: As most of you know, the design of turbo exhaust systems runs counter to exhaust design for n/a vehicles. N/A cars utilize exhaust velocity (not backpressure) in the collector to aid in scavenging other cylinders during the blowdown process. It just so happens that to get the appropriate velocity, you have to squeeze down the diameter of the discharge of the collector (aka the exhaust), which also induces backpressure. The backpressure is an undesirable byproduct of the desire to have a certain degree of exhaust velocity. Go too big, and you lose velocity and its associated beneficial scavenging effect. Too small and the backpressure skyrockets, more than offsetting any gain made by scavenging. There is a happy medium here.

For turbo cars, you throw all that out the window. You want the exhaust velocity to be high upstream of the turbine (i.e. in the header). You'll notice that primaries of turbo headers are smaller diameter than those of an n/a car of two-thirds the horsepower. The idea is to get the exhaust velocity up quickly, to get the turbo spooling as early as possible. Here, getting the boost up early is a much more effective way to torque than playing with tuned primary lengths and scavenging. The scavenging effects are small compared to what you'd get if you just got boost sooner instead. You have a turbo; you want boost. Just don't go so small on the header's primary diameter that you choke off the high end.

Downstream of the turbine (aka the turboback exhaust), you want the least backpressure possible. No ifs, ands, or buts. Stick a Hoover on the tailpipe if you can. The general rule of "larger is better" (to the point of diminishing returns) of turboback exhausts is valid. Here, the idea is to minimize the pressure downstream of the turbine in order to make the most effective use of the pressure that is being generated upstream of the turbine. Remember, a turbine operates via a pressure ratio. For a given turbine inlet pressure, you will get the highest pressure ratio across the turbine when you have the lowest possible discharge pressure. This means the turbine is able to do the most amount of work possible (i.e. drive the compressor and make boost) with the available inlet pressure.

Again, less pressure downstream of the turbine is goodness. This approach minimizes the time-to-boost (maximizes boost response) and will improve engine VE throughout the rev range.

As for 2.5" vs. 3.0", the "best" turboback exhaust depends on the amount of flow, or horsepower. At 250 hp, 2.5" is fine. Going to 3" at this power level won't get you much, if anything, other than a louder exhaust note. 300 hp and you're definitely suboptimal with 2.5". For 400-450 hp, even 3" is on the small side."

"As for the geometry of the exhaust at the turbine discharge, the most optimal configuration would be a gradual increase in diameter from the turbine's exducer to the desired exhaust diameter-- via a straight conical diffuser of 7-12° included angle (to minimize flow separation and skin friction losses) mounted right at the turbine discharge. Many turbochargers found in diesels have this diffuser section cast right into the turbine housing. A hyperbolic increase in diameter (like a trumpet snorkus) is theoretically ideal but I've never seen one in use (and doubt it would be measurably superior to a straight diffuser). The wastegate flow would be via a completely divorced (separated from the main turbine discharge flow) dumptube. Due the realities of packaging, cost, and emissions compliance this config is rarely possible on street cars. You will, however, see this type of layout on dedicated race vehicles.

A large "bellmouth" config which combines the turbine discharge and wastegate flow (without a divider between the two) is certainly better than the compromised stock routing, but not as effective as the above.

If an integrated exhaust (non-divorced wastegate flow) is required, keep the wastegate flow separate from the main turbine discharge flow for ~12-18" before reintroducing it. This will minimize the impact on turbine efficiency-- the introduction of the wastegate flow disrupts the flow field of the main turbine discharge flow.

Necking the exhaust down to a suboptimal diameter is never a good idea, but if it is necessary, doing it further downstream is better than doing it close to the turbine discharge since it will minimize the exhaust's contribution to backpressure. Better yet: don't neck down the exhaust at all.

Also, the temperature of the exhaust coming out of a cat is higher than the inlet temperature, due to the exothermic oxidation of unburned hydrocarbons in the cat. So the total heat loss (and density increase) of the gases as it travels down the exhaust is not as prominent as it seems.

Another thing to keep in mind is that cylinder scavenging takes place where the flows from separate cylinders merge (i.e. in the collector). There is no such thing as cylinder scavenging downstream of the turbine, and hence, no reason to desire high exhaust velocity here. You will only introduce unwanted backpressure.

Other things you can do (in addition to choosing an appropriate diameter) to minimize exhaust backpressure in a turboback exhaust are: avoid crush-bent tubes (use mandrel bends); avoid tight-radius turns (keep it as straight as possible); avoid step changes in diameter; avoid "cheated" radii (cuts that are non-perpendicular); use a high flow cat; use a straight-thru perforated core muffler... etc."

"Comparing the two bellmouth designs, I've never seen either one so I can only speculate. But based on your description, and assuming neither of them have a divider wall/tongue between the turbine discharge and wg dump, I'd venture that you'd be hard pressed to measure a difference between the two. The more gradual taper intuitively appears more desirable, but it's likely that it's beyond the point of diminishing returns. Either one sounds like it will improve the wastegate's discharge coefficient over the stock config, which will constitute the single biggest difference. This will allow more control over boost creep. Neither is as optimal as the divorced wastegate flow arrangement, however.

There's more to it, though-- if a larger bellmouth is excessively large right at the turbine discharge (a large step diameter increase), there will be an unrecoverable dump loss that will contribute to backpressure. This is why a gradual increase in diameter, like the conical diffuser mentioned earlier, is desirable at the turbine discharge.

As for primary lengths on turbo headers, it is advantageous to use equal-length primaries to time the arrival of the pulses at the turbine equally and to keep cylinder reversion balanced across all cylinders. This will improve boost response and the engine's VE. Equal-length is often difficult to achieve due to tight packaging, fabrication difficulty, and the desire to have runners of the shortest possible length."

"Here's a worked example (simplified) of how larger exhausts help turbo cars:

Say you have a turbo operating at a turbine pressure ratio (aka expansion ratio) of 1.8:1. You have a small turboback exhaust that contributes, say, 10 psig backpressure at the turbine discharge at redline. The total backpressure seen by the engine (upstream of the turbine) in this case is:

(14.5 +10)*1.8 = 44.1 psia = 29.6 psig total backpressure

So here, the turbine contributed 19.6 psig of backpressure to the total.

Now you slap on a proper low-backpressure, big turboback exhaust. Same turbo, same boost, etc. You measure 3 psig backpressure at the turbine discharge. In this case the engine sees just 17 psig total backpressure! And the turbine's contribution to the total backpressure is reduced to 14 psig (note: this is 5.6 psig lower than its contribution in the "small turboback" case).

So in the end, the engine saw a reduction in backpressure of 12.6 psig when you swapped turbobacks in this example. This reduction in backpressure is where all the engine's VE gains come from.

This is why larger exhausts make such big gains on nearly all stock turbo cars-- the turbine compounds the downstream backpressure via its expansion ratio. This is also why bigger turbos make more power at a given boost level-- they improve engine VE by operating at lower turbine expansion ratios for a given boost level.

As you can see, the backpressure penalty of running a too-small exhaust (like 2.5" for 350 hp) will vary depending on the match. At a given power level, a smaller turbo will generally be operating at a higher turbine pressure ratio and so will actually make the engine more sensitive to the backpressure downstream of the turbine than a larger turbine/turbo would."

 

[reboticon]

That was very informative thanks for sharing.

Question, why would you bother shelling out for a high flow cat instead of just taking it off altogether? I mean its gonna be far from street legal either way right?

 

[Telion]

good question it will only as non-street legal as they know, and putting a cat on it will keep it more compliant the places I go to will pass it so long as their computer does and it has a few key items such as an egr, a muffler, an engine that is the same year or newer and cat. Plus it is better for the environment. :hide:

 

[reboticon]

No need to :hide: we got zero emission enforcement here. Still I left the cat on my legend. Just wouldn't understand putting one on a track only car. But if it helps you get away with driving it on the street, I understand:bigok:

 

[Telion]

Ok as some of you know my laptop hard drive took an indefinate leave of absence and I am now trying to get by on 6gigs which Widows and its sub components I need take up about 5.9 of that but Iwas able to get the driver for my camera after three days and multiple viruses had to reformat a couple times lol. but here is what I have in mind for teh passenger side

Thank you for your patience

driverside is still to be worked through there's a lot less space over there.

 

[Dethred]

PERFECT!:bowdown: :bowdown:

 

[Telion]

well not yet but it is getting there. The drivers side will be a bit more work, but I think I am going to do most of the mocking up on the spare engine.

 

[Telion]

Now that the camera is back up I can also show a pic of how I re-did the power steering reservoir to provide a little more space and create a more low profile look for the reservoir. After a week or so I will update as to how it is going but so far so good ( I did have a clamp I needed to tighten down a bit and a little sealing was required).

 

[Team LR]

lookin good, your making alot of progress:thumbsup:

 

[Dv8]

Our engine bays a looking more and more similar as the days go by.


~Dv8