Michaelc

I'm interested to know what people think about the following 997.1 performance improvements and if they are worth it? IPD Plenum and 82mm throttle body, Headers and 200 cell cats. After, a possible ECM remap/flash/update. I've read about these components, but am curious to hear what people think as a package.

SoCal C2S

Is 20hp at the wheels worth $4K?

idlook2

I think you would be lucky to get 20hp at the wheels. Sell the car and buy something faster if you want more power.

Appraiser

The topic has been covered ad nauseam but our community is lacking a body of dyno sheets, I don't know why, so the discussions continue.

Some posters have debunked the performance plenum piece with dyno sheets, others vouch for it with dyno sheets and some engine builders swear by it. Look at what Porsche needed to do with the X51 package(s) and I think that's a reasonable estimate of available 'affordable' potential performance gain. Any motor ought to have another 5% in performance left in the tank.

A 200 cell cat will make the biggest difference and a muffler delete will save you some pounds and may push a little exhaust gas out quicker, it'll be loud though, data suggests the cats are good for about 5 horsepower to the wheels. If you've got a 3.8l motor ditch the factory header, the design is inferior to the sport header style like the GT3 and 3.6l, if you have a 3.6l motor don't bother - you've already got the superior design. I personally don't buy into the plenum kool-aid, I doubt the claims, but I'm buying one to test out anyways since the builders swear by it. A tune should always work at the swap of reducing engine life, figure another 10 horsepower to the wheels. Any motor will make a bigger bang by leaning out the mix. I'm personally pulling the trigger on a Softronic tune whenever they go on sale next.

Like the plenum I'm not convinced about the larger throttle body, at least not without the right software to take advantage of the larger volume of air being able to come into the intake manifold would make a noticeable difference... I'm skeptical any bench tune is going to incorporate it in a meaningful way. I haven't seen anything that suggests there's a mechanical air volume choke in our systems - it's a pretty efficient system. Same about the dual intake snorkel system; I think works for the X51 car because of the extensive software and optimized heads that use the extra air volume efficiently, in my non-professional opinion of course. I'd love to try a dual snorkel setup though!

My bias is coming from an S2000 race car I had before my 911. I ran a larger intake system with throttle body and intake manifold and exhaust - diameter's coming from the Spoon race cars. I had an AEM EMS stand alone engine management software system and dyno tuned the heck out of it. I saw about 10 hp more (217 whp) than a fresh factory F20C motor, albeit with a massive torque gain for a fat chunk of the power band. For autocrossing it was great and the throttle response quickened without a lightweight flywheel. I have not seen anyone comment about that with a competition plenum and GT3 TB. Again, I'm skeptical a bench tune will take advantage of it.


What I think our cars would benefit greatly from is a higher final drive. Enjoy the power we have in a practical way, our engines can and should be revved!

I love modding, I love installing the parts and I like experimenting to get the car just right keeping it all in personal balance. There's a lot of ground to cover between any Carrera and a GT3 RSR. Modding is a fun part of the ownership experience, it's playing fantasy race engineer - setting up the suspension components for a specific track, playing with data logging to see where you can pickup time, getting that 'zen' locked in between the whole supporting cast and crew across braking, rubber, powertrain, drivetrain, controls, suspension, chassis, driver. Some guys don't care for that - and that's fine too but they'll be sure to poo-poo on other people's hobbies. They won't be much help in this thread so pay them no mind

I think you can't go wrong with the cats, tune and aggressive/lighter muffler kit. Try to collect any data you can; be it a timed run or dyno.

idlook2

The plenum is definitely koolaid. The engine builders that frequent these forums to scare us all into thinking our engines are about to blow don't make any more power with their "built"� engines. Just look at the recent dyno sheet posted for the 3.8L car in the for sale section. It makes a whopping 290hp, that's the same as a stock 3.8L. There is very little power to be had.

https://rennlist.com/forums/vehicle-...si-engine.html

motopix

That listing and the seller's responses...I don't know, something seems off.

Don't believe the hype.

idlook2

I agree. Now don't cold start your car or it will blow up! Especially if you are using Mobil 1 and not DT40!

Backmarker

20HP at the wheels with bolt ons, HA HA

Show me a dyno that a vendor didn't have a hand in, most of this stuff is snake oil

Rather than spend money for power get instruction at the track/auto X. The driver is usually the slowest part in a 911

SoCal C2S

OK....so 18hp at the wheels for $4K.

Doesn�t make a diff at the track. Spend the money on coil overs and use the hp you got to the max.

bazhart

All dyno's vary and there are parameters that can be adjusted to change the result, furthermore with the engine position the amount of hot runs the engine gets also influences the output.

The only benefit is direct comparison and if that involves different engines or internal parts the weather and ambients will be different by the time you fit them and try again.

Acceleration is proportional to torque (not power) and operates between the revs you are in when you change gear to the revs you reach before changing again.

A thrust line showing the rear wheel torque in each gear against road speed makes this very clear and shows why the best way to get more performance is to increase torque and the easiest way to do that is to increase the capacity - because by doing so you effectively build an engine with smaller auxiliaries than it had before and this shifts the torque curve down.

Peak revs power is up a little (due to the additional piston area or stroke (or both) but mid range is much improved.

Furthermore the revs the engine drops to as you change gear is a proportion of the change in the gear ratio - so if you rev higher before changing gear - the revs drop to the next gear is greater - requiring a broader power band.

By increasing capacity - you don't have to rev quite as high to achieve better acceleration and pick up in any gear is improved.

There is an old saying that there is no substitute for capacity - and this is why.


Baz

.

idlook2

Dynos have the ability to correct for things such as ambient conditions and it is common to report the SAE corrected power.

SAE:
"SAE (Society of Automotive Engineers), USA. Power is corrected to reference conditions of 29.23 InHg (99 kPa) of dry air and 77 F (25�C). This SAE standard requires a correction for friction torque."

Michaelc

Thanks for all the input, I heavily modded a 993 and it ran a lot better. I love the way this car is stock, but have the mod bug. As it's an S I was considering the things I listed, but feel like maybe headers and 200 cell cats are as much as would be productive. Any thoughts on what headers and cats are best? I've used Fabspeed products in the past, but their are so many options these days I'm curious about what others think.

FZP

100% correct on the driver part.

rwdds

I'm fairly new to the forum, and so don't want to step on anyone's opinion. I previously tuned a few other 'sports' cars (a '94 SVT Mustang Cobra, '06 Infinity G35 Coupe) with performance related engine mods and enjoyed wonderful improvements to those vehicles. I have personally, never dyno'd but recognize the empirical, cold valuation that numbers and charts offer to many drivers.

In my 997.1S for about 7 months and because I live 15 minutes from their facility, I went with Fabspeed. I started with their dual air intake, then the 200 cel catback pipes and finally an ECM tune for now. The improvements in the torque band, throttle response and overall acceleration are very noticeable and IMHO worth every penny. I am considering the GT3 throttle body/ plenum and then a retune. but for now I couldn't be happier. If you pay attention to all of the people on the forums who have done these mods, my take is, the vast majority are quite pleased.

Appraiser

I suspect the aftermarket (Fabspeed) header design with the longer collection and slightly larger diameter will be comparable among brands using the same design, pick your poison. I would avoid factory 3.8l looking designs. They are around $1,400 with rennlist discount. Below that is the X51 design - it's OEM if that means anything to you. Typically around $1,100 when on sale through Suncoast or elsewhere, They retail for about $1,300. Occasionally they pop up in the classifieds for around $700-800. Either will be superior to the factory unit in there now.

I have no info on 200 cell cats. I've read that they are typically expensive and you want to avoid the Chinese stuff. FVD Brombacher has em for $1,800. They also do a whole package with headers, mufflers cats and tips for $6,727. There's some discussion on cross-over vs U-shape vs X-pipe, I think? No clue what the superior design is for our cars.

Either way, get a tune to accompany the cats and try to smooth out that exhaust flow (mufflers) as much as possible with similar diameter tubing. If you suspect some more air going in will be advantageous (plenum/TB/dual snorkel), which Porsche does but I think the heads have more to play in that, than grab them before the tune.

FVD, Softronic, Fabspeed, APR, EVOMS and others offer bench tunes. I suspect they are all similar if not the same in what they do. It sounds like FVD has a great reputation around here and they seem transparent about their data - I look forward to buying their baffled oil pan in the future. EVOMS has the most conservative claim (10 hp) which I find the most believable. Personally I'm going to go with Softronic simply because when I dug through the annals of this forum's HPDE/modification subs there where several posters whom seemed to be straight shooters about their car setups and had miles of track experience and they went with Softronic. Superstitious, maybe.

Dollars and cents you're in for ~$4,500 to pick up 4% power increase. That's 1/3 the price of an X51 package which adds 7% over factory. Even if you don't feel the performance difference, you'll hear it, which is worth the price of admission alone.