i was wondering how big of a bore u can go on a stock aan block? I know about tossing in a 2.5l crank for more displacement, but how about the bore?

Well the AAN starts out at 81mm, cylinder spacing is the same as the VW 4 cylinders. And velocity would punch them out to 84mm if they x-rayed good. But to be honest, on a high boost AAN the extra cylinder wall thickness is beneficial to longivity. Take this example: Audi Sport brought the bore down on the Sport Q's for this reason that's why they are 2.1's.
HTH

<center><img src="http://pictureposter.audiworld.com/70228/30lbboost_528hp.jpg"></center><p>
I am runing 83.5mm bore with the 2.5 crank.
The car dyno 528whp at 30lbs boost.

I disagree on the 2.1l statement based on block strength. The FIA uses a 1.4:1 multiplier for non-atmospheric engines. Hence 2110x1.4=2954. Which happens to fall just under 3.0l which is the max displacement for the class.

L8R

Captaudi
too many q's

whats your setup?

At least he doesn't have to round up to get 2.6L ;-)

I do remember that they had to make the 3.0L class. If that were the only reason to reduce displacement they would have used 84mm pistons and a 76mm crank since over square is better than under square. Engine longevity is why they didn't.

mod list
600 HP 2.6 STROKER MOTOR
CUSTOM CHIP SET FROM TMTEC
VMAP
JE PISTONS
EUROSPEC RODS
PORTED AN POLISHED HEAD AN INTAKE
CUSTOM EXHAUST MANIFOLD
T4 T04R TURBO
7A EXHAUST CAM
HKS 60MM WASTEGATE
EXTERNAL DUMPED WASTE GATE
HKS BLOW OFF VALVE
3" TURBO BACK EXHAUST
CGR 6 SPEED
PORSCHE 993TT FRONT BRAKES WITH A8 SLOTTED ROTORS
STEEL BRAKE LINES
ALUMINUM FLYWHEEL
6 PUCK CLUTCH
EIBACH SPRINGS
BILISTEN SHOCKS
FRONT MOUNT INTERCOOLER 3.5X28X11.5
CUSTOM INTERCOOLER PIPING
CUSTOM COLD AIR PIPING
AUTOMETER BOOST &amp; EXHAUST TEMP GAUGES
AEM WIDE BAND AIR FUEL GAUGE
BOSCH MOTORSPORTS FUEL PUMP
440 RC INJECTORS
BBS RGR 17X8
ALL MODS DONE MYSELF

Best 1/4 mile 11.9 at 123mph.
James

When audi reduced the bore of the 2.7t engine it was done to increase block stiffness. At least that is what we were taught at the intro launch in 1999 (15 yr audi tech). As far as running over square vs. under square. All of the Audi factory drivers complained about the off boost torque of the I5. Why would audi decrease this torque even further by reducing the stroke of the engine? The thing to remember is a rally engine needs to be flexible in its power delivery. Not a 9000 rpm buzzbomb with a 2000 rpm powerband. It was also much easier to work with a production crank and rod combination and fine tune engine displacement with bore size. And engine longevity was never an issue with the Audisport I5. The total number of engine failures can be counted on one hand

L8r

Captaudi

You believe what you read or were taught and I believe what I was told. I guess it depends who's source is more detailed and accurate. I just giving my 2 cents from the (original) Audi Sport tech's from the Groupe B days.

2.1 x 1.4 = 2.9l Capt audi is right on, there is no other reason for the 2.1l motor, it has nothing to do with who you spoke to. This is well documented. In fact, if you run piston speeds audisport used over the years, if it weren't for equivelency, they would have run a 2.4l I5. More trivia, if it weren't for equivelency, audi would have used the 3.6 or the 4.2v8 in WRC urq's.

This isn't worth further discussion Toxcheap, do some homework, or just do an archive search on audifans, I put a history of the I5 displacement post there 6months ago. There couldn't be more historical documentation available if you care to read it. Try getting Jeremy Walton first.

Scott Justusson
QSHIPQ Performance Tuning

So are you trying to tell me that the trans Am 200 and IMSA 90 had to be within 3.0L??

Toxcheap:
Let this thread die. This is mudding up the I5 development forum. The homogolation of the I5 into competition is not only crystal clear, it's well documented. Do some homework instead of gettting into the "who I spoke to"'s. That's a major copout without a single supporting quote or direction.

FYI II the trans am car actually had a smaller (2110) displacement than the WRC "B" cars.

Toxcheap, to get a perspective on the I5 turbo engine roots and development, you need to look at the racing rules, not necessarily Audisports wants. The rules on the I5 turbo engines, and Audisports history of following them, have very little to do with any single engine builder. It's not 'who' built it, it's what rules the engine had to satisfy.

Scott Justusson
QSHIPQ Performance Tuning

I let this this post go on and on. I post whatever the fVck I want, I'll tell people audi's were built by Yugo. There was more to the story than just the class, sorry all you know is what you read, I read that same story in VW/Porsche back in the 80's about having to make the 3.0L class in group B.
The fact is if they thought it would of held up, they would have gone bigger in Trans Am and Imsa (where they were at such a HP disadvantage) instead the went smaller hmmmm.
FIA had no part in the decisions of what configuration of stroke and bore Audi used as long as it made it's 3.0L class after the turbo conversion.

Toxcheap:
Get books. Both Trans Am and GTO were extensions of the Group 4 and Group 5 rules of FIA. As such, both these series had some basic rules of engagement wrt production car/engine basis. Certainly the GTO was most liberal in the rules here (bodywork), but by definition, it had to compete in the over 2.5&gt;3.0liter equivelency class. Trans Am was more restrictive on bodywork, but it also put the 2.1liter motor in with the over 3 liter class based on equivelency. Equivelency goes back to FIA group 4, B and Group 5 racing in europe.

Both GTO and Trans Am were competitive series seasons (unlike Group 4 and B WRC seasons)for Audi, IOW, both series would impose restrictions (or creatively enforcing rules) during the season if the cars were 'too' competitive. Thankfully for Mercury, it just didn't rain all the time.

I don't at all mind entering this thread, but it sure could have been with more educated posts. Toxcheap, I'd be more interested in details of "who" you spoke to that may shed light on contradictions to a well documented racing history of the I5.

Or, let it drop Toxcheap.

Scott Justusson
QSHIPQ Performance Tuning

Explain why the others used v8's are you saying those were 3.0L's too.

The Mercury v8 and v6 ran in the same GTO class. Get some books on IMSA GTO and Trans Am series. Three things are becoming obvious: 1) this is transgressing from the I5 development topic 2) You are not clear on any type of homogolation or equivelency rules in racing and 3) You are avoiding backing up your claim that you "spoke" with anyone regarding I5 development.

Drop it?

Thanks

Scott Justusson

definition, why would the 90q20vt car be limited to 2190cc and the multiplier of 1.4-ish for an equiv. displacement of 3.07L? That to me doesn't make sense, and is why I brought the Cougar up. I can't find the old regulations (only the '04-05 stuff), so I can't answer my own question.

The really screwy thing is that they ran the V6 (flat hood) and V8 (cowl hood) at the same events.

The #6 Cougar was running a "2500cc Turbo" at Summit Point. The #4 &amp; 5 90q20vt's were running a "2100cc Turbo". At Mid Ohio, the Camaro was running a "5500cc" V8 in GTO, the #6 and #9 Cougars the same turbo motor. The #76 300ZXt was also running a "2500cc Turbo". Using the same 1.4 multiplier, that puts the Nissan and Mercurys well north of 3.0L, and the Camaro with its V8 is definately north of 3.0L.

In 1989, GTO by definition, stands for Grand Touring "Over" 3 liters. Just about every turbo car in GTO was bumped by equivelency (reread the posts - only group 4/B FIA ran 2.1 to stay *under* 3.0L equivelency)to be over 3liters. GTO was 3.0-6.0 liters (including equivelency cars) in 1989. Trans Am was limited to 510hp, GTO was limited to 620 and worked it's way up to 720 by the end of the season.

All that said, the engine lines had to be based on production motors. Audi could meet the HP limits (and beyond) of both Trans Am and GTO with the same bore and stroke motor. The bottom end was race proven, met Homogolation rules, and was bulletproof.

Audisport could have 'extended' their welcome (cough) in GTO with the v8, but decided instead to enter it in DTM racing in Europe. Audisports brief foray into the US circuit caused quite a controversy, and the crossover to car sales in US isn't as strong as in Europe.

Follow the thread carefully above. 2.1 in Group 4/B WRC used 1.4equivelency base to keep the quattros in the 'under 3 liter class'. SCCA and IMSA used a higher equivelency to bump the cars into the 'over' class. All series had many engine restrictions, which audi could meet with the same bore and stroke that kept them in Group B. Why change something that can satisfy all rules?

More trivia, IMSA GTO required that Audi disable the 6th gear in the 6speed gearbox (forward gears limited to 5).

Hope this helps clear up the mud.

Scott Justusson
QSHIPQ Performance Tuning

Hope this clears the mud LOL you never answer a question! Double talk and technobabble at best.

Hope this clears the mud.

PS Missed you at waterfest :0P

Toxcheap, you are making this a personal battle instead of a meeting of the minds reagrding I5 development and history. Audi used the 2110cc motor in the IMSA series for 3 main reasons. First they had it, and it was a strong proven performer. Second, IMSA rules stated the engine/chassis combo had to be based upon a production vehicle. Third there is/was a cap on engine output and Audi had an engine that met all 3 criteria. Remember that GTO stands for Gran Turismo Omologato. Or Homologated for Grand Touring. This meant that all aspects of the IMSA car had to meet that criteria. If yoy have other info than what is clearly documented by both IMSA/FIA and Audisport bring it on. Just make sure you can provide solid evidance to substantiate it.

Cheers,

captaudi

I also have no problem respecting peoples requests not to be brought up in these childess threads. I only try to share with other what I learned, and if I heard that it's best to leave that cylinder thickness alone because of how great the cylinder pressures become in high HP applications would you rather I just not mention it, would that be more a meeting of the mind by your definition? I figure it like this, hasn't done me to wrong yet. Ask 2.6urs4 if he's still on his first motor.

Toxcheap:
It's not disagreement as much as it is misunderstanding. It's quite clear to me that only a few really have delved into IMSA and Trans Am Audisport efforts. Cuatrokoop was closest with the v6 and the v8 Mercury's running in the same class. Some tracks worked better for the v6, some for the v8 cars. Why?

I have a long history of correcting Audisport misunderstandings, many of them belong to you. GTO and IMSA and Group B are so well documented, you have had to contradict your own posts (first oversquare, then cyl wall thickness?). I'm quite comfortable regurgitating my dusty library, and am also fascinated by any deviations from it. IF they are valid.

When I can't pull that exact information from a guy that 'claims' to have it, 'disagreement' would be the nicest word I can think of calling it.

Peace

Scott Justusson

And you where were telling people that crap for over 10 years! Thanks again for the laugh you always cheer me up Scotty!

but i also weight 600lbs...mwahahahahhaa.

dude your car is nuts. i bow and offer my first born as a sacrafice to you.