Revamping the Rx7

That's definitely good to know.

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"The more I learn, the more I realize I don't know and have so much more to learn." - Claude Rouelle, Optimum G lecture June, 2011

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john vanlandingham
Dave,
I think some slower thinking is needed.

What you say is right up to the conclusion.

IF we believe that Setrab and Mocal know what they are doing supplying OEMs and all kinds of top world level teams for decades, they say it is the sheer VOLUME of air passing thru the cooling elements

It is both volume and temperature, but its only the volume that concerns me here. There is only so much compressor heat to dump, and any reasonably sized intercooler can be assumed to dump the same amount of heat in front of the radiator. That's not a big deal. The big deal is that air has a choice, it can either go through that big nasty stack of fins, or it can go around. The more resistance there is, the more air will just go around.

Now, given a finite grille area and a substantial cooling need, high-output cars will end up needing a deep stack of coolers. If you need them, take the advice of the cooler engineers and stack them as tight as possible. Sure, we can all agree on this.

The disconnect is here: this engine doesn't NEED nearly this much intercooler. Cutting the intercooler size in half is unlikely to change the engine performance one bit (I'm assuming stockish engine, 12ish PSI boost, 200-225 hp max, since that's what is required if you want this engine to last).

So why are we restricting radiator airflow? What's the benefit? We know radiator airflow is critical in rally, we know turbo Miata engines tend to have cooling challenges, and we know this is a lot more intercooler than is necessary for 225 hp. Sure, this might work. Or it might run hot and force you to pussyfoot through a rally. Or it might overheat and blow up.

Whatever you choose to do, don't make it easy for the air to go around. Block up every alternate path around that radiator. If the air is going around, it goes around the car. This helps a LOT.

Because bigger is always better-er-er. Bigger turbos are always better-er.
Bigger injectors, preferably at least twice as big as needed, are always better-er, and by that same inexorable logic, bigger intercoolers must be even better-er-er.

Because then no matter what you'll have more horsepowerzez.

And more horsepowerzez are always more than less horsepowerzez.

You don't get around the intra-webz much do ya?

Well as they say on better forums everywhere
SEARCH NOOOB!!!

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John Vanlandingham
Sleezattle, WA, USA

Vive le Prole-le-ralliat

www.rallyrace.net/jvab
CALL +1 206 431-9696
Remember! Pacific Standard Time
is 3 hours behind Eastern Standard Time.

well i do have smaller interfoolers around, they are just... really small. and the in/out are on the same side which sucks.


Anyway, another thing im working out. Fuel pump needs to be contained in a leak proof case if inside the hatch area. I do not wish to have it tuck under the car. SOOO would it work if i just used a metal ammo can? They are metal, leak proof, etc. I dont see why it would work.

Also, could i use plastic ones instead?

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First Rally: 2010 First RallyX: 2004 (a bunch)
Driver (0), Co-Driver (7)
Organizer (3), Volunteer (3)
Cars Built (2.5), Engines Blown (2) Cages Built (0) # of rotations (3.5)
Last Updated, Apr 9, 2023

Why not just do an in-tank pump? Is your cell not able to handle that?

the stock fuel tank is an external pump tank, so there are just three nipples welded to the top of it, no access to the inside, pretty much what so ever.

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First Rally: 2010 First RallyX: 2004 (a bunch)
Driver (0), Co-Driver (7)
Organizer (3), Volunteer (3)
Cars Built (2.5), Engines Blown (2) Cages Built (0) # of rotations (3.5)
Last Updated, Apr 9, 2023

How does the fuel sender go in the tank?

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Gravity Fed
well i do have smaller interfoolers around, they are just... really small. and the in/out are on the same side which sucks.

Got any pics of your other intercoolers?

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eyesoreracing
Why not just do an in-tank pump? Is your cell not able to handle that?

What's with this in tank pump sheeeeeut I see all over the inter-net?
Now I understand 27 year old turbo-brick virgins living at home in the basement at Mom's in San Luis Ibispo who may have lowered in one junkyard motor into the car EVER not thinking about easy access, but what would motivate making a potentially critical job (access or swap of fuel pump) harder and messier and longer?

I don't understand A LOT, but then, I'm not as smart many geniuses here.

So, what is wrong with the 2 pumps and the filter easily accessible in the spare tire well where its easy to close off?

---

John Vanlandingham
Sleezattle, WA, USA

Vive le Prole-le-ralliat

www.rallyrace.net/jvab
CALL +1 206 431-9696
Remember! Pacific Standard Time
is 3 hours behind Eastern Standard Time.

Two reasons.

1: I've never had a factory in-tank pump fail, and pump access isn't hard at all on the car I'm used to (Miata).

2: I forgot he already had pumps installed and mounted.

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eyesoreracing
Two reasons.

1: I've never had a factory in-tank pump fail, and pump access isn't hard at all on the car I'm used to (Miata).

2: I forgot he already had pumps installed and mounted.

Tom Buress was 7 miles from winning Doo Wops overall and had the single pump stop.

What I'm saying is when we give advice, we need to think not of our own possible dumb luck, but what we know people will do and then the unknowns.
People buy junkyard pumps, or run whatever junk was in their pile when they bought it and, since modern OEM pumps do seem to work reeeeeeallly well like forever, give no thought about the pump till it dies under heavy load---like when they're finally out on SS in the woods. (and shake loose sheets of rust and that blobular life form that metamorphised from the slime in the tank when the car was sitting)

THEN they discover access is shit, the in-tank connectors are shit, the metal screw on cover wants a special tool, the morphodite fuel level send contraption won't come out the hole without partial disassembly and they have no options.
And they have a frustrating time...and maybe DNF.

THEN they mount 2 pumps and a filter in the spare tire well covered with a 1/32 sheet of whatever with 3 quick release fasteners.

Difference?
maybe 1 DNF, one weekend thrown away at, these days, considerable cost...

That's why I say IN ADVANCE, plan, make access to anything absolutely vital to running the car as easy as possible, and that's mainly fuel and electrical crap like alternator, ignition amplifier--also doubled in advance.

---

John Vanlandingham
Sleezattle, WA, USA

Vive le Prole-le-ralliat

www.rallyrace.net/jvab
CALL +1 206 431-9696
Remember! Pacific Standard Time
is 3 hours behind Eastern Standard Time.



Edited 1 time(s). Last edit at 06/18/2012 02:19PM by john vanlandingham.

Alex, on your same side intercooler issue, is there any reason that you cant just rotate it 90 degrees?

I've still got one of these hangin around if you want to mess with it

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john vanlandingham

Quote
eyesoreracing
Two reasons.

1: I've never had a factory in-tank pump fail, and pump access isn't hard at all on the car I'm used to (Miata).

2: I forgot he already had pumps installed and mounted.

Tom Buress was 7 miles from winning Doo Wops overall and had the single pump stop.

What I'm saying is when we give advice, we need to think not of our own possible dumb luck, but what we know people will do and then the unknowns.
People buy junkyard pumps, or run whatever junk was in their pile when they bought it and, since modern OEM pumps do seem to work reeeeeeallly well like forever, give no thought about the pump till it dies under heavy load---like when they're finally out on SS in the woods. (and shake loose sheets of rust and that blobular life form that metamorphised from the slime in the tank when the car was sitting)

THEN they discover access is shit, the in-tank connectors are shit, the metal screw on cover wants a special tool, the morphodite fuel level send contraption won't come out the hole without partial disassembly and they have no options.
And they have a frustrating time...and maybe DNF.

THEN they mount 2 pumps and a filter in the spare tire well covered with a 1/32 sheet of whatever with 3 quick release fasteners.

So the real advice is: no matter where your pump is mounted, know the conidtion of your pump, know the condition of your tank, and know how to get to things.

If you've got loose sheets of rust in your gas tank, THAT'S your problem, not the pump location. I can get to the in-tank pump in my Miata in less than 5 minutes. Half of that time is just getting the damn hoses off.

That said, I did just reaplce the pristine rust-free tank with a rusty-around-the-edges tank full of rat turds and black widows. Hope that pump inlet sock catches all that!

Those 5000 ICs suck. Poor flow (they're double pass - it flows through half the height twice) and they tend to explode over 15psi.

They're nice starting points if you want to fab up your own ALUMINUM end tanks and make them single-pass units, though.

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Pete Remner
Cleveland, Ohio

1984 RX-7 (rallycross thing)
1978
Silence is golden, but duct tape is silver.

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aj_johnson
Alex, on your same side intercooler issue, is there any reason that you cant just rotate it 90 degrees?

I've still got one of these hangin around if you want to mess with it

I wouldn't use that one. Looks like a 2-pass cooler. air passes through the top 7 fins, turns around and runs back through the bottom 6. Total cross section of those 6 fins is pretty damn small, which means lots of flow restriction. Flow restriction=pressure drop. Pressure drop=more boost at the compressor wheel to achieve the same manifold boost. More work for the compressor means more work for the turbine. More work for the turbine means more backpressure. More backpressure means more residual exhaust gas in the cylinder. More residual exhaust means higher combustion temperature. Higher combustion temp means more knock, more retard, more cooling problems.

edit: Oh, and what Pete said!



Edited 1 time(s). Last edit at 06/18/2012 05:15PM by eyesoreracing.