Help! Design of 1969 Charger 440 Rear Dual Turbo!

[BigLime]

Hi Guys,

Newbie here for Mopar and Turbos. (Just qualifying my discussion so people don't beat the crap out of me!)

I am starting the design of a 1969 Charger 440 rear mount dual turbo setup and I really need help from not only the engine guys, but the turbo guys.

Here is my motor, which is still a mystery to some degree:

Mystery 440- Help!

As a recap, I(with help from you guys!) found out it is pretty much a stock rebuild with every thing forged. 1970 block, 30 over.
The only difference is the Speedpro (heavy) pistons and an Edelbrock Performer RPM intake with a 750 Holley car.
Cam- I don't know about until I take the heads off and measure it out.
Looks like around 9.5:1 compression based on the Speed Pro L2355f30 installed and stock heads.- Still need to CC to find out.

I am looking at the upgrades shown below. Why? I want the turbos to make up for the deficiency in the current motor. I am also lazy and don't want to change the motor too much. Let's discuss this decisions!
Also, a rear dual turbo setup will be the equivalent of a blower sticking through the hood in terms of looks and pizzazz!
NO, for those of you who will ask, I am not going to cut my hood for a blower. Also, I looked into a Procharger or equivalent, but the HP loss versus gain just doesn't float my boat.

Underhood temps are a real concern in AZ where I may be driving around when it is 110 out. With a lower HP engine like mine, I would need to have significant boost with a Procharger due the Procharger losses.

This is a street machine only, so I think that an engine that has tremendous torque in the 2500 PRM range is the best for my needs.

Engine recap as it is currently:

1. Stock bottom end.
2. Around 9:1 with the stock heads.
3. Some sort of small performance cam. The engine doesn't sound stock, but is not real lopey.
4. Edelbrock Performer RPM with a Holley 750.

Engine only upgraded I will make:

1. Trickflow 240 to get some real performance. Please comment on this. An Edelbrock performer or E-Street have much lower flow. Anything else out there that is not out of this world on price? I need to spend big money on the Turbos, described below.
2. Holley Super EFI. 1200 CFM, blow through. I think that my situation needs the ability to plug away on a computer to find the best setup.
3. Holley Hyperspark. Same reason as in #1.

So:
I have tuned the car up and am going to the Dyno to get a baseline. Not much of a tuen really. Idle screw adjusts only on the carb. My guess, per Dynosim6 is as follows:

 

[BigLime]

Hey, Who uses Dynosim to get a baseline? Anyone?

Looking for a rough baseline. Dyno will come soon on the engine currently in place.

 

[RemCharger]

What do you mean by baseline.

Are you dynoing the motor out of the car?

 

[BigLime]

So here is what DynoSim 6 show in terms of a stock engine, with a stock can shaft.

It seems like the program works "OK" giving a max of 313 HP, which is more or less in line with a base 350 HP factory 440, which is overrated (per the info. I have found on the internet).

 

[BigLime]

What do you mean by baseline.

Are you dynoing the motor out of the car?

Remcharger:
You have always been very helpful. Thank you.

Nope, just doing a seat of the pants estimate. I need to get the heads on order ASAP, since the supply chain issues suck at this point. Just looking for general comments...

 

[RemCharger]

Remcharger:
You have always been very helpful. Thank you.

Nope, just doing a seat of the pants estimate. I need to get the heads on order ASAP, since the supply chain issues suck at this point. Just looking for general comments...

There's nothing wrong with being excited about a project and jumping in with both feet...
Buuut.. my opinion is the rear turbo thing won't be as cool as it sounds. Lots of lag, loss of heat, that's why you want the turbos as close to the exhaust source as possible.
Your current engine should make in the 375 area if everything is "right".
The trickflow head plan is a great idea, and as I'm sure you know, they make 620 horse NA on their dyno mule. If you cam it right, you should be close with your current bottom end.
I built one for my buddy's car, but it's yet to hit the street. I would really like to try it out

 

[BigLime]

So here is the Dynosim with just the addition of the Trickflow 440 heads.

Max of 396 HP. This sounds reasonable to me with the added flow and the fact that I have the Performer RPM and a 750 Holley. Yes?

 

[BigLime]

There's nothing wrong with being excited about a project and jumping in with both feet...
Buuut.. my opinion is the rear turbo thing won't be as cool as it sounds. Lots of lag, loss of heat, that's why you want the turbos as close to the exhaust source as possible.
Your current engine should make in the 375 area if everything is "right".
The trickflow head plan is a great idea, and as I'm sure you know, they make 620 horse NA on their dyno mule. If you cam it right, you should be close with your current bottom end.
I built one for my buddy's car, but it's yet to hit the street. I would really like to try it out

Thanks!
I am going with expensive Garrett turbos. G25-550. Small as well as ceramic bearing to help with spool. ($3K each!). A Procharger is $7K or so... I would think quick spool would more than make up for the exhaust lag.
The intake lag is another topic. I may very well go with no intercooler and do Meth inject to save some lag. Depending on what I would assume the intercooler size would be. There is some lag there that I may be able to make up for it given the longer return line from the turbo to the Plenum. For street only, I picked these small turbos due to the huge torque at relatively low RPM. I will post this data soon.
I am running an A833 on the street. I am showing around 525 Tq at 2500 RPMs. With my 3:9 rear end, my issue will be hookup. It is always nice to smoke the tires all the way to third gear, yes?
Add a Gear Vendors and I am in nirvana! Close ratio keeping the power in the sweet spot.

Keep in mind that I am looking for a tame running car that really gets into it when stomped on. I do not want a 650 HP NA car. Super lumpy cam doesn't line up with my 60 year old age!

Your comments are always greatly appreciated Remcharger!
Dave

 

[4speed68rt]

I don't get it, too "lazy" to build a good motor, but you want to do all of those crazy mods to put 2 turbos in the back? Sounds like a good way to mess up a good car to me. Just my opinion. It doesn't sound like you are short of funding. Just build a good motor and enjoy the car for what it is. A muscle car from the '60s. Turbos are for little cars. At least don't cut it up and do any permanent damage, so the next owner can recover it.

 

[BigLime]

As a side note, I am running the HP manifolds with a full 2 1/2 exhaust with mufflers.

Funny enough, this restriction actually helps me at 2500 rpms on up as compared to a long header exhaust. Even the TTI short headers style shows a wash in terms of torque at 2500 rpm's or so.

This is a street machine and I will take all the torque I can get below the redline.
My calculated redline, by the way, is 5500. I want to maximize below this. I would think even at 650 HP (which is my desired HP), that I can run a stock bottom end forever on the street.

Torque is another issue on the whole drivetrain that I will handle later.

 

[INTMD8]

Not sure if you've ever driven a rear mount turbo setup. I have tuned several of them and I think they are horrible.

If you want power at 2500, it's really not what you want. They are super lazy down low.

 

[BigLime]

I don't get it, too "lazy" to build a good motor, but you want to do all of those crazy mods to put 2 turbos in the back? Sounds like a good way to mess up a good car to me. Just my opinion. It doesn't sound like you are short of funding. Just build a good motor and enjoy the car for what it is. A muscle car from the '60s. Turbos are for little cars. At least don't cut it up and do any permanent damage, so the next owner can recover it.

Tomato, tomatoo, or how you would spell it.

I want something cool and different but dont want a supercharger sticking out of the hood. Really nothing more than that.
I have the funds and time to do this. What else am I going to do at 60 years old? I need a project.
Keep in mind that it will look really cool and different. I searched and found that I can get the filters and silicone connections in green to match my car. Come on, that is cool right?

 

[BigLime]

Not sure if you've ever driven a rear mount turbo setup. I have tuned several of them and I think they are horrible.

If you want power at 2500, it's really not what you want. They are super lazy down low.

Were they single large turbos? Journal bearings? Lots of turns and curves in the tubing to the Plenum?

The newest, most expensive (and smaller since I want dual turbos) are ceramic ball bearing and give more than 25% less lag. If I run Meth and do not have to run an intercooler, the volume "savings" should make up, to some degree, for the added tube length back to front.

I may be totally wrong. You are much more of an expert than I am. Any and all comments are really appreciated. Please feel free to call me out if I am saying BS.

At this point I am book smart and street dumb. Not where I want to be, so I am leaning on you guys.

 

[INTMD8]

Well just a little background. I do efi calibration for a living. Thousands and thousands of cars over the last 20+ years.

I've calibrated a countless amount of turbo cars, many my own (and have built many turbo systems myself)

Basically, every desirable characteristic you can achieve with a properly built turbo system gets ruined when you mount the turbos as far away from the engine as possible.

Mount GT35R's next to the engine and the response is so fluid you would think it's naturally aspirated, aside from the massive surge of power as you roll onto the throttle.

Take those same turbos and put them at the back of the car and it feels like you're stepping into a cold pile of mushy oatmeal.....one one thousand.....two one thousand and here comes some boost. It's horrible.

I can get into all of the details why but it doesn't really matter.

The most important thing is, nothing you can do to maximize a rear mount setup will allow it to even approach the overall performance and response of a system with the turbochargers where they should be (near the engine).

Which on a 69 Charger, should be a very easy task.

 

[BigLime]

So...
DynoSim6 (Hey, who wants to comment on their accuracy, or at least an accurate baseline) show the following:

So around 700Hp or so at 5500 rpms. I am hoping for 650HP at 5500 so I went a little higher. 650 is what you guys say is an absolute max on a stock bottom end, so I went with that.

 

[BigLime]

Looking at the Compressor maps from Garrett, it looks like the Dynosim6 is in line with what I am seeing. Attached are the Garrett calc's and the Compressor maps based on the results.

 

[BigLime]

I don't think 8 or so PSi is an issue, but I am calculating 10.25 or so CR with the Trickflow heads.
Once I CC what I have, we will see. My issue is that if I have to use a thicker head gasket that I might be compromising the head seal. Comments?

 

[BigLime]

Well just a little background. I do efi calibration for a living. Thousands and thousands of cars over the last 20+ years.

I've calibrated a countless amount of turbo cars, many my own (and have built many turbo systems myself)

Basically, every desirable characteristic you can achieve with a properly built turbo system gets ruined when you mount the turbos as far away from the engine as possible.

Mount GT35R's next to the engine and the response is so fluid you would think it's naturally aspirated, aside from the massive surge of power as you roll onto the throttle.

Take those same turbos and put them at the back of the car and it feels like you're stepping into a cold pile of mushy oatmeal.....one one thousand.....two one thousand and here comes some boost. It's horrible.

I can get into all of the details why but it doesn't really matter.

The most important thing is, nothing you can do to maximize a rear mount setup will allow it to even approach the overall performance and response of a system with the turbochargers where they should be (near the engine).

Which on a 69 Charger, should be a very easy task.

Thank you for your input.
I just see no where I can put the turbos in the engine bay without making a huge mess and drastically increasing the under hood temps. Any comments are appreciated!

 

[BigLime]

Not sure if you've ever driven a rear mount turbo setup. I have tuned several of them and I think they are horrible.

If you want power at 2500, it's really not what you want. They are super lazy down low.

Crap! Even with smaller dual turbos that are ball bearing?

 

[INTMD8]

Crap! Even with smaller dual turbos that are ball bearing?

Yes. (and ball bearing doesn't make a huge difference) The Garrett stuff seems the best for response but more so due to less weight than bearing configuration).

The turbos you're looking at are too small for a 440 unless you want it to lay over at under 5k.

Smallest I would use is GT3076r (and mount them under the hood).

I've built systems on very tight engine compartments so I don't see the challenge with doing so on a B-body.

Could probably do a quad turbo system under the hood if you wanted.