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RD - Not directly related to CTS-Vs but in my import days we put a lot of effort into trying to keep as much heat and velocity as we could upstream of the turbine. Granted we were working with a lot less displacement, fewer cylinders, etc so trying to minimize lag in a turbo that would feed enough CFM and efficiency to feed 500+hp. I’d imagine the same would hold true here as well, but maybe less life or death since the engine is still generating a lot of torque to carry the turbo into spool up?

Packaging is also a huge deal. That is the primary reason I’m getting my heat management under control on the blower, finalizing the tune and putting the car up for sale. I’m ready to jump into something with a little more area under the hood to be able to focus on trying to maximize efficiency and performance and less on packaging limitations.


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I've seen a few Corvettes with turbos mounted close to the rear axle that made lots of power and were very fast.
So would I be wrong stating; you feel that mass flow, is the key to performance regarding a turbo…
 

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RD - Not directly related to CTS-Vs but in my import days we put a lot of effort into trying to keep as much heat and velocity as we could upstream of the turbine. Granted we were working with a lot less displacement, fewer cylinders, etc so trying to minimize lag in a turbo that would feed enough CFM and efficiency to feed 500+hp. I’d imagine the same would hold true here as well, but maybe less life or death since the engine is still generating a lot of torque to carry the turbo into spool up?

Packaging is also a huge deal. That is the primary reason I’m getting my heat management under control on the blower, finalizing the tune and putting the car up for sale. I’m ready to jump into something with a little more area under the hood to be able to focus on trying to maximize efficiency and performance and less on packaging limitations.


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So then your goal seems to surround the retention of heat, which
then generates a pressure, thereby generating a mass flow.

That mass flow rate, also contains a velocity component, which
you also feel is important. . .if I’ve read your post above correctly.

RD
 

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Yes sir. I’m sure we are oversimplifying the weight each of these things carry in effecting a quick spooling car. I definitely wasn’t part of a high end race program, just a tuner shop for Honda’s that liked to drag race as a hobby with a couple of road race cars that were competitive.


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Discussion Starter #485
So would I be wrong stating; you feel that mass flow, is the key to performance regarding a turbo…
Bruce,

I'm not speaking for anyone here but myself, but yes. You want as much heat trapped in the exhaust to create pressure and more flow velocity. That being said, You also have to properly size the turbos to a given setup that also aligns with your goals. Like choosing a cam. Do you want a turbo that spools fast an can generate 500 CFM of flow, or do you want a turbo that generates 1,000 CFM of flow, but doesn't do so until 5-6,000 engine RPM.

What you are getting at with your questions is correct. It is greatly dependent on platform too. My car for example, Looks like a normal car and can be used to take my kids so school. I didn't want exhaust coming out of my fenders or hood. That being said, the turbos have to go somewhere and that somewhere is by the transmission bell housing. Knowing how far they are away from the exhaust ports, was a factor in the turbo selection. I knew I would never run larger than a 62mm turbo since my goals are sub 1,000WHP.

Each of these turbos are being fed by 3.5L of displacement....not some little baby 2.0L.

I actually ran a single T62 back in the day on a Pontiac Grand Prix GTP. Engine was 8.5:1 CR, 231CID. Stock iron heads, but with a healthy cam. Car went 11.4 @ 120 + (I can't remember the exact MPH) and weighed 3,200lbs. This was a FWD setup and getting out of the hole was tough. You want to talk about shitty exhaust ports.....reference the L67 engine's heads....horrible.

Both the exhaust banks fed the turbo on that setup. I noticed a difference in spool quickness after I had the manifolds jet hot coated inside and out. That kept the heat in and exhaust gas velocity up.

Another way to do it is to set your exhaust valves on fire. J/K....but not really. If you reduce ignition timing you can torch your exhaust and spool your turbo fast that way. I'm talking about doing so within reason......this is where Inconel exhaust valves come into play.

Glad you brought up this topic, I think a lot of folks building turbo setups might not know the correlation between exhaust heat and velocity and the affect on turbo turbines. Additionally, reduced ignition timing having a huge impact on EGT.
 

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Discussion Starter #486
I feel like I'm not telling you anything you don't already know and fully understand. :)
 
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I feel like I'm not telling you anything you don't already know and fully understand. :)
Oh yeah, haha. I feel like my anecdotal, trial and error based experiences would still only broach maybe half of what Bruce could figure out with math and his overwhelming knowledge of cutting edge ICE performance.

I assume your wastegates are recirculated too? If so, that entry back into the exhaust stream can help or hurt turbo performance too when looking for the level of refinement you seem to strive for.


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Oh yeah, haha. I feel like my anecdotal, trial and error based experiences would still only broach maybe half of what Bruce could figure out with math and his overwhelming knowledge of cutting edge ICE performance.

I assume your wastegates are recirculated too? If so, that entry back into the exhaust stream can help or hurt turbo performance too when looking for the level of refinement you seem to strive for.


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The WGs are dumped. Free cutouts! lol.
 

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I feel like I'm not telling you anything you don't already know and fully understand.
Actually I am simply looking for the reasoning for installing the
turbos so far from the exhaust port.

Yes, I understand the packaging restraints, and I think if you tie
that in with Jim''s statement below, you might have the answer.

I've seen a few Corvettes with turbos mounted close to the rear axle that made lots of power and were very fast.
You also stated:
That being said, the turbos have to go somewhere and that somewhere is by the transmission bell housing. Knowing how far they are away from the exhaust ports, was a factor in the turbo selection. I knew I would never run larger than a 62mm turbo since my goals are sub 1,000WHP.
So this tends to tell me the issue of heat is not lost here, and that
some like yourself are simply accepting the compromise. . . .

Cheers,
RD
 
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The other issue I have with remote mount turbos at the back of the car is the amount of tubing to pressurize back up every time the blow off valve opens up. For drag cars, it’s probably less of an impact but for street driving and road course with more throttle modulation it has a more noticeable impact to transient response. The transient response is what most people notice more than the initial lag.


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Anyone else have anything to add?
 

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The other issue I have with remote mount turbos at the back of the car is the amount of tubing to pressurize back up every time the blow off valve opens up. For drag cars, it’s probably less of an impact but for street driving and road course with more throttle modulation it has a more noticeable impact to transient response. The transient response is what most people notice more than the initial lag.


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Well written post my friend. . . .

Generally speaking; heat accomplishes the work, but a mass flow
rate and a pressure differential are also required.

When heat is present you have expansion.

So now you have a temperature differential.
The higher that temperature differential is, the greater the potential will be.

-however-
If there is no pressure in the exhaust system, then the turbine
will not move, and no work will be accomplished. . . . .

Doesn't matter what the temperature is.

Having say. . . .4-atmospheres of pressure in the exhaust system
is much better, than is only 1..lol

If you only had an ambient pressure of 14.7 psi on the inlet side,
but you had a vacuum on the outlet side, the turbine would spin, but
not much work would be done.

I once again restate my opening sentence:
Generally speaking; heat accomplishes the work, but a mass flow
rate and a pressure differential are also required.

Cheers,
Bruce
 

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Discussion Starter #493
So this tends to tell me the issue of heat is not lost here, and that
some like yourself are simply accepting the compromise. . . .
Cheers,
RD
Yes, totally accepting the compromise. I can do this more easily than some as this is a toy....no racing for $$$ or competing for a trophy. The only trophy I deserve is, meanest person to street tires.

Now, once someone comes out with headers for turbos, that actually fits, I might pull the trigger. This will still place the turbine housing by the transmission bell housing.
 
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Discussion Starter #494
So, made more progress today.

Let me say, clocking and installing these turbos is a huge pain in the butt. Not a lot of room and they are having to be installed in parts and assembled while installed....which is difficult.

I said enough and decided to order shorter oil inlet/restrictor fittings. The ones provided were tall and did not allow me to clock the cartridge properly with the oil drain at the 6 o'clock position. It hit the turbine housing. I ordered a couple that have crush gaskets and fit much closer. Hopefully they will clear the turbine housing.

147934


The supplied oil lines seem very tight and I also had enough of that mess, so I bought some quality 4AN feed lines with the fittings already on them.

147935


Got the LS3 intake manifold ported. Now the 102MM TB clears and the runners are ported to match the heads as much as they can be. I wanted to retain the factory gasket recessed spaces on the runners, so I didn't go all the way into them. Better than not touching it at all.

I ordered black manifold bolts to go along with my black everything look. Those will be here Tuesday and then I can finally bolt the intake down.

Tomorrow I'll install the electronic boost controller and pick up the silly amount of vacuum line needed.

My new 90Deg coupler came in today and it needed a little trimming to fit, but now the maf clears the flipped TB. It also fits over the water pump hose right there....I was worried about that as they are smashed up against each other.
147936
 
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Discussion Starter #495
I forgot to add....I got the crash bar installed on Saturday. That and the FMIC. Grade 10 hardware and steel spacers for the FMIC to it didn't hit any of the radiator/AC parts.
147937

147938

147939
 
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So, made more progress today.

Let me say, clocking and installing these turbos is a huge pain in the butt. Not a lot of room and they are having to be installed in parts and assembled while installed....which is difficult.

I said enough and decided to order shorter oil inlet/restrictor fittings. The ones provided were tall and did not allow me to clock the cartridge properly with the oil drain at the 6 o'clock position. It hit the turbine housing. I ordered a couple that have crush gaskets and fit much closer. Hopefully they will clear the turbine housing.

View attachment 147934

The supplied oil lines seem very tight and I also had enough of that mess, so I bought some quality 4AN feed lines with the fittings already on them.

View attachment 147935

Got the LS3 intake manifold ported. Now the 102MM TB clears and the runners are ported to match the heads as much as they can be. I wanted to retain the factory gasket recessed spaces on the runners, so I didn't go all the way into them. Better than not touching it at all.

I ordered black manifold bolts to go along with my black everything look. Those will be here Tuesday and then I can finally bolt the intake down.

Tomorrow I'll install the electronic boost controller and pick up the silly amount of vacuum line needed.

My new 90Deg coupler came in today and it needed a little trimming to fit, but now the maf clears the flipped TB. It also fits over the water pump hose right there....I was worried about that as they are smashed up against each other.
View attachment 147936
With all the hassle you're describing... What are your thoughts on going with the Comp oil-less, air cooled turbos?

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Discussion Starter #497
With all the hassle you're describing... What are your thoughts on going with the Comp oil-less, air cooled turbos?
I could not do it. I'm ok with the PITA, because in the end I'll have a solid oil system for the turbos. Just have to get the right parts to clear all the hot parts.
 

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Fair enough. Either way, I'm excited for updates. Hopefully soon I'll be able to get my Huron Speed kit installed. I jumped on the revised kit when they released it back in June, and it all finally arrived a few weeks ago.

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Fair enough. Either way, I'm excited for updates. Hopefully soon I'll be able to get my Huron Speed kit installed. I jumped on the revised kit when they released it back in June, and it all finally arrived a few weeks ago.
Yeah, the revised kit looks bad ass for sure. I need to fab a couple or strut bars that connect the cradle to the frame. Not sure what I'm going to do exactly, but I know I'm going to use a steel tube of sorts. It felt good cutting those out....so much room for activities now.....well, until the air filters go on.

When are you starting the install? What turbos did you decide to go with and what other engine mods do you have? Still SBE?
 

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Yeah, the revised kit looks bad ass for sure. I need to fab a couple or strut bars that connect the cradle to the frame. Not sure what I'm going to do exactly, but I know I'm going to use a steel tube of sorts. It felt good cutting those out....so much room for activities now.....well, until the air filters go on.

When are you starting the install? What turbos did you decide to go with and what other engine mods do you have? Still SBE?
I went with Comp oil-less air-cooled 6264s. I have a Don Hardy Racing built LSA, still 376. Don built the motor specifically for twins, with the solid roller cam ground to match the heads for the twin application. I've been driving it for almost 2 years NA, while I waited for the Huron kit. In addition to the built motor, I've got the Fore triple pump system with hydramats, the flex fuel sensor and ID1700s, so when it's boost time, E85 will feel right at home.

Not sure when I'll get into the install, as life is pushing me to possibly move again in the next year or so, this time I'm finally going to buy the big tract of land I want and build on... So I'm not spending extra cash on anything right now, until I figure that out.

Once I do install, I'll likely have to build the tranny and get upgrades axles at least, haven't decided on the driveshaft and rear end. I've got the WXM rear diff cooler, and so far it's in good shape. It's still a blast to drive, even if it REALLY needs boost... I'm making stock power right now without it, but right before it was stolen I had just done heads and cam and was hovering around 700rwhp, so stock power feels slow. But at least I've got three pedals so the fun factor is still up there. Lol.

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