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advances and real-world testing that would have been done by members in the meantime, I fear some of that may be outdated.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...

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 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