GT3 Modification ability? Attention Steve!

Take a look at the following specs of the GT3 and GT3R race cars posted on the Porsche Website under Motorsport Worldwide Sales. The GT3 race car has 390 hp and the GT3R has 435hp. Wondering how possible is it to modify a road version GT3 to the GT3R specs - if at all. I read the specs myself but dont quite understand everything. If a mechanically inclined member can give us some insight that would be appreciated. Notice alson under the GT3R specs they have FIA restrictors and mention ACO power ratings are available upon request. Doe sthis mean that the motor is capabale of more than 435hp? Thanks.RR Engine GT3 Race Version flat six-cylinder boxer engine 3,598 cc, stroke 76.4 mm, bore 100 mm dia. max. torque: 390 Nm at 6,300 rpm max. power: 287 kW (390 BHP) at 7,300 rpm max. rpm: 8,000 rpm four-valve technology water-cooled dry-sump lubrication two-stage resonance intake manifold central inlet air duct electronic engine management system MS 3.1 sequential multi-point fuel injection required fuel quality: 98 octane ROZ, unleaded race exhaust system with lambda-probe-equipped catalytic converter rear silencer with twin-branch centre tailpipe Engine GT3R flat six-cylinder boxer engine, water-cooled 3.598 cc, stroke 76.4 mm, bore 99.99 mm dia. max. torque: 395 Nm at 7,200 rpm max. power: 320 kW (435 BHP) at 8,250 rpm with 2 x 30.8 mm dia. restrictors in FIA version (power ratings in ACO version: at request) max. rpm: 8.500 rpm four-valve technology oil-cooler (oil-water heat exchanger) dry-sump lubrication under pressure oil and cooling water refilling system intake manifold with single throttle valve, with 2 x 30.8 mm dia. restrictor electronic engine management system MS 3.1 Bosch MS 3.1 fuel injection with ignition control required fuel quality: 98 octane ROZ, unleaded race exhaust: multiple pipe manifold, open exhaust, no catalytic converter (rear exhaust muffler retrofit)

The GT3R has open exhaust,no cat, probably gets 9mpg (highway) and the engine has to be rebuilt every 10,000 miles.

I think we all know it has an open exhaust and no cat it states that... What I want to know is what parts are put on the GT3R are we able to add/replace with on the GT3 eg. The GT3 seems like it has one throttle valve for all 6 cylinder where as the GT3R has one throttle valve for EACH cylinder. FVD used to sell kits for NA993's to replace the stock throttle valve with a throttle valve system for each cylinder. With that mod they were able to get 30hp. Wonder if it applies here to the GT3.

Hi, I'm still new to the board and trying to figure out which car I want (!!) but based on the specs you provided, the higher horsepower of the GT3R appears to be due "simply" to the higher rpm's. Disregarding units, if you take the power and divide by the rpm's, you get approximately the same "factor" for both cars. This is basically saying that with similar torque, you get higher HP with higher rpm's. So the GT3R basically gets a higher HP by virtue of an engine capable of higher rpm's. Andy

</font><blockquote><font size="1" face="Verdana,Tahoma,Arial,Helvetica,Geneva">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Arial,Helvetica,Geneva">Originally posted by RR: <strong>Wondering how possible is it to modify a road version GT3 to the GT3R specs - if at all.</strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Arial,Helvetica,Geneva">I don't see why not. I would say, if time and money are no object, it can be done. OTOH, it may be much less expensive to replace the car with a GT3R.

check out cargraphics 3.9 conversion for the gt3.it was in gt purely porsche magazine a few months ago.numbers are 415hp and 415 nm of torque,the car in the article also had gt3r linkages,ratios and rear differential.german magazine sport auto did some testing with results = 0 - 62mph in 3.8 secs , 0 - 100 - 0 in 12.5 compared to a standard cars 14.4 secs.with a power to weight ratio of 321 bhp per ton. hope this is helpful i just keep the article round its a good read. cheers

could you post that 3.9L conversion article, please? Thanks, Grant 03 GT3 waiter

Are we talking about a street car? From the 3R's that I've seen (and I've only seen them at race tracks) the engine is not going to be street friendly at all. I think it's possible but you are likely to be disappointed with the way the thing idles after spending close to $60K for such a conversion, maybe more.

From what I understand, the GT3 street and cup motors are similar but the GT3R is an entirely different beast built with much tighter tolerances which is why it needs to be rebuilt frequently. It's really not a matter of swapping some parts out to turn a GT3 street/cup engine into a GT3R. Just so you know, the GT3R motor (last I checked) was running almost twice as much the street version. I was getting quoted about $60k for just the motor.

Kyopo has it right. Assuming PMNA would either sell you the GT3R engine parts or, more likely, have you send the engine to them for the rebuild, you could never street the car. Not only do they require a rebuild after about 30 hours of use but they won't pass emissions and have to have at least 100 octane gas. You would also have to swap out the DME and wiring harness, and maybe some other stuff as well. These engines don't idle well, wouldn't like sitting in traffic and are very tough to start when cold. Totally impractical as a street engine. If you want more HP, buy a Turbo. They are much easier to tune via software. Karl

"Octane ratings are different in Europe. I believe a European 98 is equivalent to a US 93." The above was a quote I pulled from an archive. Can anyone verify this? If thats the case then the GT3R will use US93 octane, becasue as you can read in the stats the GT3R and GT3 both specify 98 ROZ fuel,as I pulled those stats from the Great Briatin site and not the North American sites. Also can anyone verify ACO power ratings which are mentioned on the GT3R specs?

Europe uses RON (Research Octane Number) to rate their gasoline. US uses (RON+MON)/2 (Research + Motor)/2. The RON is determined with a test engine running at a low speed of 600 rpm. The MON is determined with a test engine running at a higher speed of 900 rpm. Generally the MON is ten points lower than the RON. So a RON 98 fuel should give you (98+88)/2= 93 Octane by US rating.

The specs may state that the engine will run on 93 octane but you won't find anyone on the grid of any race event with either a GT3 Cup or a GT3 RS that is running 93 octane. It doesn't matter anyway because the other points still apply - it's not emissions legal, rough idle, hard cold start, frequent rebuilds. Any way you cut it, this is not a street car engine. There is a guy in the UK that is written about in almost every issue of 911 World. He owns a legitimate GT3 street car and has converted it to GT3R specs over the last couple of years. He changed the body and the suspension but he hasn't done anything to the engine except the usual bolt on stuff like headers, exhaust, intake, etc. This guy is serious about getting as close as possible to a GT3R for the street and seems to have money to burn. If he didn't attempt a conversion, that should tell you something. Karl

</font><blockquote><font size="1" face="Verdana,Tahoma,Arial,Helvetica,Geneva">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Arial,Helvetica,Geneva">Originally posted by Karl S: <strong>The specs may state that the engine will run on 93 octane but you won't find anyone on the grid of any race event with either a GT3 Cup or a GT3 RS that is running 93 octane. It doesn't matter anyway because the other points still apply - it's not emissions legal, rough idle, hard cold start, frequent rebuilds. Any way you cut it, this is not a street car engine. There is a guy in the UK that is written about in almost every issue of 911 World. He owns a legitimate GT3 street car and has converted it to GT3R specs over the last couple of years. He changed the body and the suspension but he hasn't done anything to the engine except the usual bolt on stuff like headers, exhaust, intake, etc. This guy is serious about getting as close as possible to a GT3R for the street and seems to have money to burn. If he didn't attempt a conversion, that should tell you something. Karl Karl</strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Arial,Helvetica,Geneva">Karl, in Europe for the cup races and most club events, the 98 European (= 93 US spec) is manadated so everyone runs with it. I have to tell you that when the temperature in GA or FL was below 80F, I also ran my cup car with 93 US gas and never had any pinging or loss of power that was noticeable to me. I also had no one with similar cars pull off from me under these circumstances....

One could, given time, money, environmental and vehicle licensure laws allowing you to do it, convert a GT3 to GT3R specs. The entire parts book for a GT3R (or even the Carrera Cup GT3) represents a treasure trove of performance modification bits for a street GT3. It would be *VERY* expensive and you would perhaps be better off to buying a GT3R in the first place if the exact car was your target. <img border="0" alt="[typing]" title="" src="graemlins/yltype.gif" />

RR; You have surely received some great advice here; I'll confirm that the GT-3R and RS race engines are not streetable and of course, cannot pass any smog tests. Having rebuilt a few GT-3 Cup engines, there ARE ways to get more power out of the GT-3 engine that helps bridge the gap between the two. We are in the process of installing a real GT-3 engine & transmission into a 996 (as well as suspension & brakes) and this will be OBD-II compliant, when we are finished.

I have a question for all the guys wanting to mod a car they are on the waiting list for: How would it benefit you to put forty grand in a car that already has 380 hp(and costs 100k)? It seems that it would be much easier to but a turbo (120k) and spend three grand on a chip/exhaust, etc. Even if you want a psychotic thrill ride, you could pick up a GT2 (456 hp) for 150k right? and you won't worry about emissions or rebuilds on those cars nearly as much... I guess I just can't wait to have that kind of change.

Steve... The GT3R seems to have (correct me if I am wrong) 6 throttle control valves ie 1 throttle valve for each cylinder making a total of 6 control throttle control valves. Look under the GT3R stats on my first post, which was copied from the Porsche Motorsports section of their website, it states the following: "intake manifold with single throttle valve" Which I take to mean one throttle valve per cylinder. Where as the GT3 cup car and road car seem to have only 1 throttle control valve ie 1 throttle control valve for the entire set of 6 cylinders.(which is the norm in most vehicles) I do know that FVD offers single throttle control valves for the 993 which resulted in 30 more HP for the 993. Would this upgrade not do the same for the GT3. I wish everyone would get off the rhetoric of assuming that any mods would make a GT3 smog illegal, unless you know for fact. Steve seeing that you have worked on GT3 motors can you shed light on this? Thanks

RR: Indeed, the racing versions; GT-3R and RS have a 6-butterfly throttle bodies under the dual plenum resonance chamber intake manifold. The GT-3 street and Cup cars use a single throttle above the dual-plenum resonance chamber intake manifold. Assuming that one had the $$$$$, one could fit the RS intake system to the Cup or street version but it would take remapping the ECU's throttle maps for that. The main benefit for the 6-throttle intake is sharper throttle response when using race type camshafts. These have closer lobe centers and longer duration than Cup or street cams, and creates the intake reversion that plays havoc with any single throttle manifold. With all due respect to FVD, my experience runs counter to a larger throttle making a 30 HP increase on a 993. Porsche did a fine job on the 993 engine and even the 3.8 RS intake uses a throttle that is almost identical to the other Varioram engines. 993 Cup cars used a single throttle intake, sans MAFS, and they only made 315 HP with horrible drivability. My advice is to stick with the stock intake and find that 30 HP elsewhere since that is possible to do,....

Thanks Steve. Ok so how else can you improve the 380hp on the GT3. I know that FVD was getting just over 400hp from the 1999 GT3, which was a 360HP motor. Does the GT3 come with equal length headers? Also the 1999 GT3 came with a dual mass flywheel, whereas the Clubsport came with a single wheel, lightweight flywheel. Do you know what the 2003 model will be fitted with?

</font><blockquote><font size="1" face="Verdana,Tahoma,Arial,Helvetica,Geneva">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Arial,Helvetica,Geneva">Originally posted by RR: <strong>Thanks Steve. Ok so how else can you improve the 380hp on the GT3. I know that FVD was getting just over 400hp from the 1999 GT3, which was a 360HP motor. Does the GT3 come with equal length headers? Also the 1999 GT3 came with a dual mass flywheel, whereas the Clubsport came with a single wheel, lightweight flywheel. Do you know what the 2003 model will be fitted with?</strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Arial,Helvetica,Geneva">RR: There are internal modifications that one does,.... GT-3's do not have equal length headers; a high quality set such as the S-Car-Go ones do help along with a good race muffler setup. IMHO, its too loud for street use without cats. I do not know for certain which flywheel the GT-3 will come with but my best guess (given that its going to be OBDII compliant) would be the dual-mass one.