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Discussion Starter · #1 ·
Recently I had the bad idea of putting one of Audis longitudinal 5 cylinders into an FD rx7 for Gridlife ClubTR, and in researching the options, that raised some questions. Before I list them, here are some of the rules that are effecting my choice:

-All vehicles must retain stock chassis with no fabricated

-Modifications (such as large unibody modifications) Minor modifications to facilitate engine swaps are allowed.

-Bolt on alternate materials may be used for Hood, Trunk and Hard Tops but shape must remain generally true to OEM.

-Dogboxes / sequential gearboxes prohibited , Dual clutch automatic style transmissions are allowed only when factory equipped in the car used in competition (no swaps).

-E85 is permitted, as are pump-sourced gasoline options up to 93 octane. No other alternative fuels are allowed. [I would prefer to run 91-93]

-Factory internals are specified as pistons, compression ratio, rods, camshafts, head and block casting, bore and stroke size and head porting (example: K24 swap ok, K24 block with k20 head not allowed, etc). Machining of engine internal components to gain advantage is not allowed (porting, decking or milling for compression, etc) . Other engine pieces are allowed to be modified (better oil pumps, oil pans, intake manifold swaps, etc.)

- Factory twin/sequential turbo rotary engines (FD rx-7, etc) are not eligible for Club TR / Street Lite.

-Forced induction cannot be swapped INTO any vehicle.

-OEM (single turbo, or single supercharger only) forced induction vehicles under 1.6L are allowed when using completely stock turbocharger and exhaust manifolds, as equipped on that specific VIN chassis [NA size limit is 2.5L]

-Drivetrain changes are prohibited, i.e., FWD to AWD or AWD to RWD.

Ive been looking around and see that there are 2/3 main longitudinal 5 cylinders, the AAN, 7a, and the 2.0 from classic Quattros. Has anyone done a NA build of an AAN? Is an NA aan functionally the same as a 7a? Was a rwd trans made for any of those 3 engines? Were any widely sold in the US? Does the AAN have stronger internals than the 7a? Do 5 cylinders rev decently fast? Do AANs have much NA support? Are 7As more optimized towards NA functionality? I probably should have stated this, but my HP goal is 250-300 rwhp, though I do not know if that is going to be through a stock RX7 5 speed or something else.
 

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1990 Coupe Quattro (3B, K26/K27, VEMS), 2007 S8
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I'll take a stab at this, you've come to the right place for fans of the Audi I5 engine, in its many variations. Search these forums for a wealth of knowledge, but traffic has been slow as of late.

Has anyone done a NA build of an AAN?
Someone probably has, there are all kinds of crazy people out there. Only reason (other than "for fun") that I can think of is if your 7A engine blew up, and the only replacement engine was an AAN and you didn't mind losing power.

Is an NA aan functionally the same as a 7a?
Basically, yes. The engine blocks are very similar, essentially identical. Different pistons and bore. The AAN went to a distributorless ignition system, so the cam timing sensor is in a different location (at the cam sprocket), but still just a single window hall sensor. Oil pan is different because they went into different chassis cars. AAN has a serpentine belt setup for its accessories, which are mounted in slightly different arrangement. Intake is different. Different camshafts with the 7A having higher lift and durations.

Was a rwd trans made for any of those 3 engines?
Not from the factory. But plenty of folks have welded the center diff and simply not connected the front driveshafts in order to convert to RWD.

Does the AAN have stronger internals than the 7a?
No. Same crankshaft, which is forged. Bore is slightly smaller in the AAN to yield 2.2l displacement vs 2.3. Pistons are different on AAN to provide lower compression which was necessary for forced induction of this era. Rods are same dimensions. If not the same, then at least interchangeable. For high power turbo builds the rods become the weak spot before pistons or crank.

Do 5 cylinders rev decently fast?
I think redline is like 7200rpm. Can be made faster but probably requires internal modifications to be reliable.

Do AANs have much NA support?
There isn't much support for any classic Audi I5 anymore. There isn't any dedicated support to convert the AAN to NA that I know of, but any parts that work with the 7A should work on the AAN. 034motorsports still has some stuff.

Are 7As more optimized towards NA functionality?
In the sense that it has higher compression and cams with higher lift, yes.

I probably should have stated this, but my HP goal is 250-300 rwhp, though I do not know if that is going to be through a stock RX7 5 speed or something else.
Lofty goals. Factory crank HP from the 7A was 164hp. Without touching the internals, you are left at modifying the intake and the exhaust. The throttle body and intake on the 7A already flow very well for what the head can handle, so your restrictions are theoretically in the MAF/filter/ducting. Minimal gains by removing all restriction there, at least in the normal RPM range. The factory exhaust can be improved. The factory 7A came with two different exhaust setups, one using a cast manifold, and another using a header (search "bag-of-snakes"). The header is more sought after but not sure if it improves flow all that much. With a custom install like this you would probably use just a straight pipe after the header, which would remove some of the factory restriction. OEM was a 2.25 pipe, going to 2.5 is all you need for NA. That leaves RPM as your main factor in pumping air and fuel. The crank, rods, and pistons are probably up for the task of a modest increase (maybe). You will probably reach the limit of the valve lifters and valve springs first. If these are allowed to be modified you might be able to bump the RPMs somewhat. Getting to 250 rwhp would be very impressive and into territory few have achieved even with massive internal modifications that seem prohibited by your rules.
One of the reason there is little info on this is that most folks in the Audi world that want big power will simply go with the forced induction options provided by the factory. The engines are robust, and by "simply" turning up the boost (and all the things that come with that) you can double the factory power before needing to touch the engine internals.
 

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Discussion Starter · #5 ·
Basically, yes. The engine blocks are very similar, essentially identical. Different pistons and bore. The AAN went to a distributorless ignition system, so the cam timing sensor is in a different location (at the cam sprocket), but still just a single window hall sensor. Oil pan is different because they went into different chassis cars. AAN has a serpentine belt setup for its accessories, which are mounted in slightly different arrangement. Intake is different. Different camshafts with the 7A having higher lift and durations.
Thank you for the clear response, Ive seen people on old S4 forums (IIRC) say they're the same but no one gives specifics on how.

[/QUOTE]
Lofty goals. Factory crank HP from the 7A was 164hp. Without touching the internals, you are left at modifying the intake and the exhaust. The throttle body and intake on the 7A already flow very well for what the head can handle, so your restrictions are theoretically in the MAF/filter/ducting. Minimal gains by removing all restriction there, at least in the normal RPM range.
[/QUOTE]

This could explain the other comment about April fools, I am used to hearing that stock setups, especially on older cars, are very restrictive. Average class hp seems to be 200-250, so with tuning and some skill, it could still be competitive.

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The factory exhaust can be improved. The factory 7A came with two different exhaust setups, one using a cast manifold, and another using a header (search "bag-of-snakes"). The header is more sought after but not sure if it improves flow all that much.
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I saw a picture of one of those on an old thread about a 2.0l 20v build, and ive been wondering what its called, it looked beautiful.

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With a custom install like this you would probably use just a straight pipe after the header, which would remove some of the factory restriction. OEM was a 2.25 pipe, going to 2.5 is all you need for NA.
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Thats what I was planning to do to get it running, though I was hoping a bag of snakes (or something like that) would fit in the bay. Ideally I would keep as much as the stock Mazda parts, maybe linking to the stock exhaust system for ease of use and mock up purposes.

[/QUOTE]
That leaves RPM as your main factor in pumping air and fuel. The crank, rods, and pistons are probably up for the task of a modest increase (maybe). You will probably reach the limit of the valve lifters and valve springs first. If these are allowed to be modified you might be able to bump the RPMs somewhat. Getting to 250 rwhp would be very impressive and into territory few have achieved even with massive internal modifications that seem prohibited by your rules.
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Wow, would that mean the turbo adds 50-75 hp?

[/QUOTE]
One of the reason there is little info on this is that most folks in the Audi world that want big power will simply go with the forced induction options provided by the factory. The engines are robust, and by "simply" turning up the boost (and all the things that come with that) you can double the factory power before needing to touch the engine internals.
[/QUOTE]

That makes sense, it sounds like a similar story to the 2JZ.
 

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Five-cylinder engines has a crank with 72 degree angles (except for the VW V5, which has an offset the crank that corresponds to the angle between the cylinders; despite the V configuration the engine has even firing intervals). Most (Audi 2.5, VW 2.5 R5) five-cylinder engines have the firing order 1-2-4-5-3.
 
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