Blow through turbo charging

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ryderfmjones21
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Blow through turbo charging

Post by ryderfmjones21 » Thu May 09, 2019 1:11 am

Has anyone got any experience on blow through turbo charging a u20?
My current set up it’s a rebuilt u20 with dellorto carbs, stock cam, new valves and Springs, and an digitally controlled distributor.

My question is based more on exhaust routing, turbo, intercooler placement, oils line routing, and what kinda jets and needles should be used in the carbs.

I will most likely use a turbo from an older mr2 and I was wondering if I could use the oil cooler kit to feed oil through the turbo instead of a oil cooler. Though that sounds risky to me... I’m trying to get around making holes in the block...

This is all a thought in my mind at the moment. I’m only 18 so I have a lot of time to dabble!

Just checking out there for any other ideas or to see if it’s been done before. Any input would be appreciated!

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Gregs672000
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Re: Blow through turbo charging

Post by Gregs672000 » Thu May 09, 2019 11:01 am

There is one turbocharged Roadster on this list. There are many issues to consider, not the least of which is the stock compression ratio... that will limit the amount of boost you can safely run, especially since you're going to be relying on carbs and not EFI. Also, not a lot of room for a blow through system, considering you would have to have some kind of sealed air box fabricated to cover the throats of the carbs. A single suck through carb mounted sideways may be more practical, and the carbs would not have to be turbo ready (Dellortos are excellent carbs for blow through systems though, I have them).

I've kicked around a turbo R16 idea for some time, using an adapted EFI system and a log style intake. As noted there is at least one turbo U20, and I'm sure he'll have lots of insights!

If you're looking for more power, one could consider a different cam if you're running an A cam, or consider a NOS system... that works too if the engine is set up properly. My friend Sean (Captain Canada) ran NOS on this well built U20 and had no trouble challenging high powered cars. Then there was the supercharged U20 Craig Hooper had built...

In the long run, if it's only power you're looking for, then maybe an SR20 DET is the way to go...
Last edited by Gregs672000 on Thu May 09, 2019 7:11 pm, edited 1 time in total.
Greg Burrows
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ryderfmjones21
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Re: Blow through turbo charging

Post by ryderfmjones21 » Thu May 09, 2019 12:35 pm

I’m probably leaning towards the more “cool” factor as a reason why. I want to challenge and see if I can make something like this work.

As for connecting the carbs I was thinking I make a plate that bolts on and use tubing welded to it that feeds air into each port and have them all conjoin into a single large inlet connecting to the turbo. Somewhat like a header..
I was also floating the idea of the turbo being on the distributor side of the motor and relocating the battery though I’m not sure how that extra length of the tubing would effect it.

I do work in a cnc shop so making custom components isn’t a far shot!

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fj20spl311
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Re: Blow through turbo charging

Post by fj20spl311 » Thu May 09, 2019 12:44 pm

Turbo chargers are low oil pressure system. There is a restrictor in the inlet and they vent to a gravity drain or a suction pump if mounted low.
If drilling a hole in the oil pan or block is the hold up, you are not ready to design and install a turbo system.
For the money, NO2 is the cheapest system to add. My second choice would be a small blower because of ease, but lots of $$$$ because hard to get used parts.
You might be able to install a turbo low in the drivers wheel well or under the car outside the frame. I have seen systems were the turbo is near the rear axle. Both of these would need a suction pump to return the oil.
Phil
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fj20spl311
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Re: Blow through turbo charging

Post by fj20spl311 » Thu May 09, 2019 12:53 pm

If you work in a machine shop, add a super charger on the right side.
Phil
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ryderfmjones21
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Re: Blow through turbo charging

Post by ryderfmjones21 » Thu May 09, 2019 2:43 pm

Any thoughts on the amr500 super charger? Used on some bugs and Subaru’s. Reading up on it says it could produce around 5-10lbs of boost depending on the pulley set up.
Seems like the right amount for a mostly stock motor.
I have no experience on any of this. Kinda just testing the waters.

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Alvin
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Re: Blow through turbo charging

Post by Alvin » Thu May 09, 2019 4:48 pm

I would pick Mark (datsunrides) brain as he built a turbocharged (EFI) U20:
viewtopic.php?f=2&t=5310&start=135#p190700
Image
Image

Blow-thru setups were very common in the 70's/80's so any L-series based system could be adapted, ie in a 510:
Image
Image
Alvin Gogineni
San Jose, CA
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Gregs672000
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Re: Blow through turbo charging

Post by Gregs672000 » Thu May 09, 2019 7:25 pm

But there's just not a lot of room for an L-series style set up, at least I don't think. A super charger would be far simpler I think. The kind that look like a turbo. You could go EFI with a mega squirt system, use a stock SU manifold with individual injectors drilled in, mount the SC on the passenger side and plumb the Boost through a small water to air intercooler to the two SU intake throats, and keep boost reasonable and tune carefully. If you wanted you could drop compression a bit with different pistons. I bet it would be a hoot!

With the SC, there's no turbo lag, no worry about oil returns, excessive heat, etc.
Greg Burrows
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ryderfmjones21
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Re: Blow through turbo charging

Post by ryderfmjones21 » Thu May 09, 2019 8:15 pm

As cool as fuel injection would be I think I want to stick with the dellorto set up I’ve got. Spent a lot getting those anyways..
I just like the look and feel of a carbureted engine.
My goal is to do all of this but keep it as mechanical and simple as possible.
Similar to something they would do if it was still the 70s
I think I’ll have enough room to make some sort of air box or “manifold” to feed into the carbs. Though it would have to be quite compact.
I do like the super charger idea. Seems to be a bit simpler

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datsunrides
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Re: Blow through turbo charging

Post by datsunrides » Thu May 09, 2019 9:14 pm

My 2c on a blow thru setup. I may be wrong, but I would think you can’t just build a “header” or plenum and bolt it to the inlets. Wouldn’t that cause the bowls to pressurize and just dump fuel out the overflow? I think the whole carb assembly needs to be sealed, which has its own challenges. You also would probably want a boost referenced pressure regulator to keep it fed under boost, but not sure how that works with carbs that may be pressure sensitive. I know it’s “doable”, but those are just a couple issues that made going to fuel injection a better choice for me. That said, there were a few guys calling me nuts for what I did, so if you got the skills to pull it off, go for it, the information is out there. Also, as a warning, take a good look at the pic Alvin posted of my engine. That is just a little T25 sitting there with no dual carbs. The steering shaft takes up a bunch of good real estate on that side. Maybe if you re-routed the steering shaft with some ujoints that could open some room to put the turbo under the intake? For a low boost application, an intercooler is not a requirement. I probably didn’t need one since I’m currently only running about 6lbs, but I just wanted to get that 5 pound bag as full as I could. :lol:
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fj20spl311
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Re: Blow through turbo charging

Post by fj20spl311 » Thu May 09, 2019 10:03 pm

ryderfmjones21 wrote:
Thu May 09, 2019 2:43 pm
Any thoughts on the amr500 super charger?
Too small. Its a 0.5L displacement, with 16,000 RPM limit.
You would get no boost with a 2:1 ratio drive on a 2L motor.
It needs to be 1.0 L or bigger blower.
Examples:
On a 500cc two stroke, with the blower being driven 1.5:1 with the crank, it would produce approximately 7 psi boost.
On a 750cc four stroke, with the blower being driven 1:1 with the crank, it would produce approximately 5 psi boost.
On a 750cc four stroke, with the blower being driven 1.5:1 with the crank, it would produce approximately 15 psi boost.
On a 1000cc four stroke, with the blower being driven 1.5:1 with the crank, it would produce approximately 9.5 psi boost.
On a 1600cc VW engine, with the blower being driven 2.1:1 with the crank, it would produce approximately 5 psi, but the engine RPM must be limited to 8000 rpm.
Phil
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fj20spl311
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Re: Blow through turbo charging

Post by fj20spl311 » Thu May 09, 2019 10:05 pm

Blow through dellorto carbs is known art, nothing new there.
Phil
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Alvin
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Re: Blow through turbo charging

Post by Alvin » Thu May 09, 2019 10:07 pm

"Plasmaboy" supercharged his U20 using an MR2 blower unit
Alvin Gogineni
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ryderfmjones21
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Re: Blow through turbo charging

Post by ryderfmjones21 » Fri May 10, 2019 12:01 am

This is starting to sound like a monumental task! But I’m up for it. A lot more is going into this then I initially thought.
I can see how the bowls could get pressurized and dump fuel out the carb.
You guys know a lot more about this then I do.
That’s why I’m asking!
I’ve found a picture with the same concept

https://i.ytimg.com/vi/hbLgo5_fp68/hqdefault.jpg
Not exactly sure how to use this forum still...

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redroadster
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Re: Blow through turbo charging

Post by redroadster » Fri May 10, 2019 9:09 am

Whats does a turbo do to the insurance ?
(Federaly its.... unlegal)
One of the scary-fast cars (Datsun cars) I drove was a 72 Z with a crown turbo kit ...blow thru...I
wound not recommend it
Last edited by redroadster on Fri May 10, 2019 1:24 pm, edited 1 time in total.