Streetable 700whp 997.1TT, stock motor, 91 oct & 7000+ ft DA - doable or pipe dream?
 

Howdy folks.

So I've been doing a whackload of reading on the forum over the past few weeks.... but given constant advances and real-world testing that would have been done by members in the meantime, I fear some of that may be outdated.
PTF's in-house and customer GTX3076 builds have been most interesting, as well as the EFR7163 build done on Dhalhen's (sp?)car

I'd like to gauge the potential of a 997.1TT 6MT given a particular set of environmental variables, and see whether it would be feasible as a build, or an absolute dog to drive...

As per the topic, environmental variables are:

• Denver, CO type conditions. 5500ft above sea level, 90°+ summer days with 30-40% humidity at worst... So call it a 7000-8000ft DA in summer.
• ECU will see approx 830mbar atmospheric pressure, so turbo's would have to flow an extra 2.5 psi right off the bat just to hit a given absolute target.
• 91 Octane (R+M) / 2 - or 95 RON pump fuel (No E85 available, and would like to avoid constantly having to run race fuel or having to switch maps)
• No emissions regulations
• 27k mile stock 09 Cabrio, 6-speed Manual
• Car has a virtually new stock clutch, so it should hold up to Phase 1 mods given a more gradual, tapered boost request <5k RPM
• Would very much prefer to retain stock management
• Stock motor - so I'd rather be conservative with mid-range boost and torque, than bend rods.
• Street driven car, for general screwing around and the occasional 60-130 pull... Might see 1/4 & 1/2 events, once in a blue moon.
• Budget is obviously a consideration. Used items / cheaper & equally effective alternatives would be great.

So, given this, the intention would be to effect the ugprades in two phases. (Upgrades listed in intended order)

PHASE 1 (targeting 520-550 whp):
Catless X-pipe 3" exhaust, custom-fabbed
BMC panel filter
COBB Accessport V3 + Custom Tune
997.2 Intercoolers
IPD Y-Pipe
do88 Turbo inlet pipes
IPD Plenum + 82mm TB kit
Aquamist Water/Meth Injection
18-ish PSI, taking into account the deficit that has to be made up to compensate for altitude.

PHASE 2 (targeting around 700 whp):
Sachs Stage 2.5 clutch
Retain 997.2 IC's, unless not advisable? Else Champion / AMS / do88 Big pack, I suppose.
1000 / 1300cc Injectors
Colder plugs
Pinned coolant pipes
New Lambda probes & MAFs
EFR7163 / GTX3076 turbo's with electronic boost controller
Headers
External BRV's
Mapping by PTF or similar
21-ish PSI & 7400 RPM rev limiter

I'm not keen on building the motor... If a 3.8 forged rods & pistons motor build is a must, for Phase 2, then I'd rather cap proceedings at Phase 1, and upgrade to a 997.2 TTS at some point later down the line, to run a setup like longboarder's 7.2 TTS from a few years back.


Stock, the car sees full boost around 3500 RPM in 1st and 2nd gears, and just south of 3000 RPM in the higher gears when rolling on at highway speeds... I'm hoping the custom exhaust will bring down the boost threshold, as per reports on the forum - but I realize it's also a function of altitude and air density. Given that the bigger EFR7163 / GTX3076's make meaningful boost from 3500 RPM, and are spooled to full mid 20's PSI around 4500 RPM based on what I've seen at the forum, I'd expect 500-700 RPM higher boost threshold and full boost points at altitude...

I'd have liked doing 65/68mm VTG upgrades, but as per my understanding, given the conditions, they just wouldn't make the horsepower target reliably & consistently, and nor would they offer much (if any) spool advantage over the larger aftermarket turbochargers.

So, on to the questions:

1. Does anyone at high altitude have prior experience with a setup like this, and is it worthwhile given implied driveability impact?
2. Is there a better turbo solution for the 700 whp target?
3. Are 997.2 IC's the tool for the job? Or should one just go Champion / AMS straight off the bat? I'm concerned about their restriction / pressure drop, making the stock VTG's to just work harder in Ph 1, and the end tanks holding together in Ph 2.
4. Order of mods - is there anything I'll need to do earlier / later, or not at all?
5. Anything that I'm missing? Please weigh in if you've got any experience / advice.

Thanks in advance!

Bawb

TL;DR
997.1TT 6MT
Stock motor, stock management
91 octane, 5500ft altitude, 830mbar atmospheric pressure.
Targeting 700whp - Will EFR7163 / GTX3076's work, or will they make it a laggy dog of a car?
Will 997.2 IC's do the trick, or do I need to look aftermarket?
Should I just stop at Ph 1 and rather get a 997.2 TTS later down the line?

i think you are on the right track. i would skip the 997.2 ICs. go straight for the do88 big pack with inlet pipes and y pipe or AMS, you will not lose any spool here. i like and have had good luck with the Forced Performance / Xona turbos so their XR6156 would be a GT30 sized turbo, GTX3076 Gen 2 is very nice too... both will make 700whp at 19-20 psi easy and spool even better than stock VTGs. for bypass valves I use Tial QRJ that's their newest fastest responding BRV.

Cooing is crucial for hitting your target power: I've had the stock, Do88 small, and Do88 big pack. If you're on a tight budget, my recommendation is Do88 "small" pack intercoolers (and inlet pipes), along with a water/meth injection kit

Great, thanks for weighing in... you've obviously been around the block a few times on the M97 platform. ;)

I'd seen mention of and been trying to find data on the Xona's, but for some reason thought they were a direct GT30 derivative. Either way, I'm familiar with FP products - they've got some really innovative stuff.

Similarly, GTX3076R Gen 2 looks fantastic - based on the compressor map, 700whp on a pair of those, should fall right bang in the middle of the optimal efficiency, with loads of headroom. I'm assuming a .63 A/R would be par for the course, given only 1.8L of displacement driving it?

PS - I'd never seen your signature until registering today (always read on my phone) - those are some utterly bonkers performance numbers... :eek:

Yep, I realize that... The main reason I was leaning towards 997.2 coolers, was simply a price/performance ratio... They're cheaper even than the small do88's, and probably perform within a few degree... but as I've said, I'd want to spend the money once, do the fitment once... so I'd then be inclined to just go for the do88 big-pack straight off the bat, as it would include a Y-pipe as well... it just means it would take me a month or two longer... landed and cleared in South Africa, that kit would run me a rather un-fun $4300 or thereabouts.

I've been offered a used set of SRM coolers + silicone hoses for $1200, which I think is very reasonable - but I've read conflicting reports regarding their effectiveness... they'd probably cost me $1700 landed & cleared.

Another option, would be these 4.5" units from Markski... https://www.6speedonline.com/forums/...ml#post4763544

They're used, but they're local - so no shipping or customs shenanigans, and I can get them fitted while the exhaust is going on... Just need to get a spare set of hoses I can butcher to fit them onto the IC with T-clamps.

How would these compare with the Big-pack do88 / AMS / SRM coolers in terms of performance? Once again, I'm a bit in the dark -- I can't find much of anything specific about their performance on the forum, but Markski's stuff in general seems to be very highly regarded.

Once again, opinions / empirical data would be most welcome.

I have a pretty hot stock turbo setup, and while the 997.2 ICs were fine for a two-gear pull, IATs would destabilize after that and start heading for the sky. The Do88 big pack fixed that. Temps hardly rise above ambient on multi-gear runs (unless you're doing something like a half mile race). Do88 occasionally has 20% off sales, and that's when I grabbed mine. I would strongly recommend going with at least those based on your goals. No point in doing the intercoolers twice. Also while not hard, the IC install on these cars is annoying. Do it once ;)

The intercoolers would probably be fairly close. Markski uses Bell cores, they are a quality piece and for that amount of money I would jump on them. The SRM coolers are good value for the price new. I run the 997.2 coolers on a modest 1.2 bar setup in my 996tt. They are good for a road course type of setup but not as good for drag or highway racing. 997.2s are limited to modest boost levels or the end tanks blow off. The altitude should not hold you back too much, just spin the turbos higher. At your 700hp level you will likely need to upgrade your fuel pumps. Also at that level you are running some risk of pushing a head gasket. I pushed mine at the top of 5th gear at 1.3 bar. The high power stock engine build can be done, but if you aren't really committed I would just stay at that 600hp mark. I run my car around there and am very happy with it. It's best to choose a tuner that you like and go with one of the setups he has a lot of experience with. Good luck.

IllI recommend do89 intercoolers

​​​​​​And Garret new G25 turbos... They spool nicely.

And ESmotor tune to ice it off :)

This is my car specs: Cobb+TCU by ESMOTOR, Kline catless 70mm, HPTurbo VTG's 66mm, Forge DV's (yellow), DO88 Big Pack with IPD 82mm Y-Pipe oversized/dimpled, 82mm Throttle Body, IPD Plenum 82mm, complete 80mm intake piping from oem airbox to VTG, BMC airfilter.

Emre said that if i decided to add meth then ~750hp is possible. Even stock VTG is amazing on meth.

Thread below has gold information:
997 PDK Esmotor
Although is a 997.2 PDK, the power numbers increase on the 3.8 is similar to our 3.6. Performance not so much because of PDK advantage.

Phase 2 is very open ended, but Phase 1 will not get you 520whp. I ran virtually the same spec, and made around 580bhp at the fly, 480 at the wheels, so a 100bhp increase from stock (487 fly/402wheels). The car did 0-300 in around 30, 100-200 6.4. The stock turbos cannot flow anymore. GT2 based VTG's are the next upgrade but are very costly, so going to a wastegated turbo setup can make sense from that perspective.

Rick

I thought that sub 6.5s 100-200 was a 600hp (flywheel) car???
And i've seen sub 6s with stock VTG on meth... pure meth injection and not 50/50 water/meth.

I am sure with pure meth and just the right conditions you could drop to sub 6 but it isn't going to be easily repeatable. I did that in 4th only, 3rd - 4th was the same but it was a slow shift at the time. I think with your altitude you are going to struggle to reach a genuine 520WHP but the mods you suggest are spot on.

Rick

Rick, not my thread :p BTW, i'm at see level and my best was 6.1s with mods listed below on pure 98RON. Time corrected by Emre when doing ecu adjustments.

OOps, sorry. Are the VTG's GT2 based or the standard items? I have a car with virtually that spec, (larger VTG 997 base) and running no meth it makes 587 bhp on UK 98. With 50/50 643bhp. 100-200 with no meth is a touch slower than yours but it's a manual. I am currently tuning another car, a TIP which is the same but on GT2 based VTG. Currently no meth it's at 615bhp, meth yet to be tuned and so then i will provide 100-200 times,

Rick

Standard VTG. I asked in another thread without any answer: Does the 991GT2RS VTG bolt on 997.1? Any advantages over 997GT2?

I like to keep the vtg to avoid using boost controllers, external wg's... but spending 5k for less than 50hp is crazy. 991GT2RS has 700hp from factory so i would expect a increase of +100hp and that is more easy to swallow the cost ;p

It's a good question and the information is very difficult to obtain. But they are a Porsche only part and the price is quite a bit more thank 5k!

Thanks for quoting my thread... I hope it's useful to everyone 👋 :)

New gen VTGs from 991GT2RS are not exactly directly bolt on... Emre is doing a car, a 991... But again they are not very complicated to fit.


But... I hear the price is so crazy that going with a Garret setup is way cheaper.

where u gonna get 991 GT2RS turbos for 5k? they cost more than that a piece ..

:eek: :eek: :eek:

Turbo cyl 4-6

Turbo cyl 1-3​

But how much is a complete wg turbo kit for 750hp (headers, turbos, exhaust piping, oil/water piping, wastegates, boost controller...)? Under 15k?

15k is just turbos delivered to your door. they are not direct Bolton. I forget the specifics but water or oil lines are different and these have a huge vband exhaust hotside unlike the regular stockers so they wont fit stock location exhaust.

As others have said, skip the 997.2 intercoolers. The main thing is not to do things twice. So don't buy anything that doesn't meet your phase II requirements. If that means you just have a wait while you set the cash aside it's worth it vs. redoing things.

Call Robert at Forced Performance (He is half owner of Xona) and tell him what you're trying to do. He'll get you the right turbo out of the FP/Xona/Tial catalog.

Do you know if 992TTS has 991GT2RS VTG's? If yes then this should drop their price due to higher production..

That car doesn't officially exist yet does it?

Right.... slippery slope, engaged.

I've purchased the Cobb AP V3 from @turboslut with the half-off custom tune offer from @SamboTT@ByDesign - many thanks to both of you gents. My buddy in Nashville has received the package, and will be bringing it back to SA for me next weekend.

I was sorely tempted to pull the trigger on the AMS Alpha intercooler kit at the same time, but ultimately I couldn't expect my buddy to lug something that bulky around in his suitcases.

Shipping from Europe is cheaper than the US, and the friendly folks at do88 cut me a hell of a deal on a bundle of goodies, so I've procured the following:

997.1 Big Pack - Coolers + Y-Pipe
Turbo Inlet Pipes
Cast Plenum for 82mm GT3 Throttle Body

Now I'll need to figure out turbo and injector upgrades... Still leaning towards a set of the used 63.5mm Proto's in the for sale section.... but if Sam could have his way, I'd probably wind up with XR 980's and a massive hole in my bank balance.

Oh, and while we're at it... a Sachs 2.5 clutch kit probably wouldn't hurt either. :rolleyes:

First of all i'm no engineer. I had a healty discussion with DO88 about their Y-Pipe some time ago. My car has the IPD oversize y-pipe (61mm diameter and 82mm outlet), GT3 82mm throttle body size and IPD competition intake plenum 82mm . Stock y-pipe is 54mm with 74mm outlet. DO88 y-pipe is 70mm with 74mm outlet.

They was trying to make me belief that their y-pipe was better than my IPD and to buy the complete big pack. This made me think that despite the y-pipe diameter from each 2 pipes, the flow will go out by just one exit to throttle body. So atleast, you would want that the area of each pipe to be half of the area of throttle body connection.

DO88 y-pipe is made for stock throttle body 74mm. If you want the 82mm throttle body they will supply a silicone reducer from 82mm-74mm to connect throttle body to their y-pipe.

So i went back to times of school, grab a paper and calculator and start calculating circle areas. Got this numbers:

Stock Y-Pipe IN vs OUT +6.10% in
(2x54mm pipes vs 74mm)

DO88 Y-Pipe IN vs OUT +44.12% in
(2×70mm pipes vs 74mm)

IPD Oversize Y-Pipe IN vs OUT +9.65% in
(2x61mm pipes vs 82mm)

And 82mm outlet has +18.56% more area than 74mm.

My conclusion was that DO88 y-pipe will always bottle neck at oulet 74mm, despite even going larger after to 82mm TB. So i bought their DO88 big pack with connections to stock y-pipe size and kept IPD system with true 82mm diameter between y-pipe and intake plenum.

Sorry if my feedback is wrong but that made me sense at that time.

Update time... so, after finding out that the engine needs to be dropped in order to remove the stock turbo inlet pipes (and would have to be lowered anyways even just to hack them out :rolleyes:), I re-evaluated my options...

I did say from the start that I only intended on dropping the engine once... so cue Sam doing a deal for me on a Sachs 2.5 clutch kit and ID1300 injectors.

Be still, my aching credit card.

Now I just need to get the 82mm throttle body and a GT2 Slave kit, but those are cheap enough locally.


Interesting, thanks for your input.... Are you positive you're comparing the DO88 unit here? I'm a bit skeptical about that info, as the outlet looks significantly bigger than that in their pictures.

Have a look here:

https://www.do88.se/bilder/artiklar/...0SV-do88_1.jpg

If the two merging pipes are 70mm, then there's no way that outlet flange is 74mm, unless there's some serious perspective distortion at play...

But even in the event that it is in fact 74mm, I understand your viewpoint, and if one were to go for a really high horsepower application, I suppose the 74mm outlet could be a limiting factor.

However, seeing as the majority of the gain in fitting a Y-pipe comes from a lower pressure drop and an improved merge collector, I reckon the real world net difference between the IPD and do88 items would probably be academic at best.

However, if I'm wrong, and my setup underperforms, then I'll know where to go looking for a power upgrade. ;)



Edit to add: I mailed Isak at @do88 earlier to enquire, and I just saw his response:

So it would seem that the do88 outlet is in fact larger in diameter than the IPD... I'll measure it myself once it arrives next week (with a bit of luck) and advise.

I just wanted to interject to the thread starter that when you install the AMS intercoolers you do have to modify the plastic housings that the intercoolers sit in so going back to the stock ones will require some zip ties or buying new housings - probably not too expensive =left
=left
As far as an intercooler the AMS has proven to be world class in my testing - my AIT temps are always ice cold as close to ambient as you can get =left
=left
Only disadvantage is given the proximity to the turbos etc when you are not going through air - e.g. in traffic they do start to pick up soak which is quickly resolved as soon at you hit 60 mph or more they cool right down again =left
=left
I would not try and save money on intercoolers - the Garret cores in the AMS units are about as good as you can fit in the stock location - they are good for way more power than I will ever make =left
=left
Finally - unless you are going to build the motor and go with something than can spin much more than the factory rev limit or with a much larger displacement I would think that VTG turbos can get you all the performance you would ever want with minimal lag =left
=left
In my situation - even on my pump gas map I am blowing the tires off in 2nd and 3rd gear at 21 psi of boost and on E85 it is totally insane - pushing the limits of the stock rods with ease =left
=left
Here is a short video clip of my car in action yesterday

Car in the video above has poor boost control - you can hear it.

Care to clarify that statement and point out to how it would compare to “good” boost control?

If you listen to when it comes on boost, you can hear it oscillating. It's really common on VTG's and needs a lot of tuning to get right.

I would be happy to show a data log - the boost is very stable - if anything I think you are mistaking the sound of the tires spinning and grabbing which the car does in gears 1 - 3 in sport mode when it comes on boost - it is very hard to get a handle on anything as the car is all over the road in the rear end - (you have to have it pointed straight ahead)

Could well be wheels spin yes but it sounds like the vanes moving. If you have a log and it's all good then case closed :)

Update time

It's been a rather expensive month and a half, automotively speaking...
Unexpected additional maintenance on the 997.1TT,
a blown turbo on my S7 - necessitating RS replacement cores, of course :D,
and I've managed to total the wife's E70 X5 - first car I've written off in 20 years of driving. So that'll be an F15 X5 upgrade for her, thank you very much... :rolleyes:

So, the 997 went into the local Porsche indy shop to get all the parts fitted in the first week of April

All was well, until fitting the 2.5 clutch... turns out the chattering I'd heard coming from the engine bay was due to a sketchy dual mass flywheel - the sprung core had gone bad and when turning the secondary by hand, it felt spongy & very slow to return to the base position.

So, in went a lightweight flywheel (AASCO I think), sprung clutch disc + the supporting guide tube and release bearing... All for cheaper than the cost of an OEM DMFW locally (which would have run me around $2200)

While they were at it, I opted for replacing all the coil packs as well, as the car was still running the factory set from 10 years ago - most of which had started cracking where the shaft meets the body (that's what she said :p )... apparently a sign of impending not-too-distant failure.

On the bright side, all coolant lines are still firmly located in the block - so apparently there might be some truth to 09's being less prone to this issue.

So now, as it stands, the car's running the following:

Custom de-cat 3" exhaust
Do88 Big Pack intercoolers
Do88 Turbo Inlet Pipes
Do88 Y-Pipe + 82mm Plenum
GT3 82mm Throttle Body
BMC flat panel filter
Injector Dynamics ID1300x2 injectors
Lightweight flywheel, sprung clutch, 764 pressure plate
Cobb AP v3 with OTS Stage 3 1300 91 octane map

I've had it back for 2 weeks now, and I'm very impressed with the difference.

It's markedly quicker to spool the turbos, and way more responsive in general... acceleration is rather, uhm, brisk. I'd guess it's making in the region of 470-ish whp.

Frankly, I'm starting to doubt again whether to go all out for Xona XR980's or GT30's... a set of 65 or 68mm VTG's may be just what the doctor ordered - ultimate peak horsepower figures be damned.

Of course, there are a few niggles... mostly down to mapping. The Cobb off-the-shelf map is pretty darn good, but it's hardly perfect. The car is an absolute pig on fuel now, and initial throttle tip in can feel a bit "wooly", for want of a better word - particularly on the cold start map. Also, the accelerator input curve is a tad aggressive for my liking. I'm sure all of these things can be addressed with a custom map though, hence I've already thrown some cash Sam @ ByDesign's way for a custom map, that I'll start logging for over the weekend... hopefully there's another 20-30 whp on the table on pump fuel.

Also, the new flywheel and clutch setup has been a bit of a learning curve, necessitating finesse and steady feet with minimal throttle input to get off the line cleanly without either stalling it, or revving the engine up like some teenager driving stick for the first time - this is very much at odds with my former quick-blip-and-go approach on the stock DMFW - and it doesn't suffer poorly modulated 1st-2nd and 2nd-3rd shifts kindly when you've got your foot pinned and chasing the limiter

And of course, there's the stalling issue when clutching in at RPM or messing up a standing start - particularly when running the AC. It's immensely frustrating, but I'm sure it can be addressed through mapping.

I can understand why a lightweight flywheel on the 997.1 TT is so polarizing.... it makes you work harder and sucks in traffic, but also makes it more rewarding when you get it right.

All-in-all, I'm happy as things stand - the car is a hoot to drive, and will get even better going forward.

I'll post some pics when I pull them off my phone.

Oh, and as a side note... I'm pleasantly surprised with the Do88 intercoolers - I would imagine they'd remain unflappable up to some very high horsepower numbers.... I've logged inlet temps, and the efficiency is remarkable. Inlet temps will hover at around 12°C above ambient temperature during normal low speed driving, and will then actually drop down to around 4°C above ambient over the course of a 40-100 mph run...

Cool update and build though I think you have a typo in your hp # above (470) -- seems that setup would be throwing-down more like 670 or 770 (?). My car with lesser (stage2) mods dynoed at 547...

The upgraded S7 must be a blast as well. I considered an S6 or S7 as a daily a while back when my S4 finally gave up.

It's on stock turbos and 91, 470 is bang on.

Thanks!

Though, frankly, after reviewing some logs, even 470 whp seems a bit optimistic... judging by the MAF readings on a log I did last week (but only downloaded today) - where it only flowed around 410 g/s between 6000-7000 RPM, conventional wisdom of 0.8g per horsepower would suggest peak numbers of probably more in the region of 440 whp (520 crank hp)... so perhaps the Stage 3 OTS tune is a little more conservative than they're claiming - or other factors like timing and VE not telling the full story.

It feels significantly stronger than stock (410 whp for most stockers, give or take), subjectively speaking - but I've changed so much hardware in one go, and there's so much more torque from 3500-6000 RPM thanks to the mapping, that it's somewhat difficult to compare apples vs apples in peak hp numbers.

I suppose I'll need to go do a 60-130 run or a virtual dyno to get a more accurate guesstimate of what the car's making now. Or I could just go and slap it on an actual dyno. :p

Stock 997.1 turbochargers apparently max out around the 480-500 whp on pump fuel - and could probably push 530-540 whp when tuned aggressively on E85... at 5000ft altitude where I'm running it, and our relatively crummy 95 RON fuel, the upper limits are anyone's guess.


S7 is the perfect daily driver - I love that thing... APR Stage 2, full decat exhaust and SRM intakes saw it make around 500 whp. Oversize RS turbo's should make a bit more on the Stage 2 file, but should then be capable of up to 600whp on a Stage 3 map... Once again, the altitude variable might impact the ultimate number, so we'll see.