TheOtherEric

So I've decided to either go TPC supercharger or Protomotive bolt-on Stage 1. I'd like to hear some more opinions about which makes the most sense for an 80% track car. Let's start with the basics:

Other options.
A. 9M heads would be a great choice, but ruled out due to cost, especially considering today's exchange rate. Don't produce as much power, either.
B. Dropping in a 993TT engine was also ruled out due to cost. $22k for engine, less $7.5k for mine, plus $2.5k for install, amounts to $17k. But there could be other risks & costs, as you could be inheriting some problems and deferred maintenance issues.

Prioritized requirements:
1. Don't damage my engine. I.e. no detonation in 90F temps on track. Intercooler a must.
2. Reliable for track use.
3. Cost ($ per hp). Goal of 350 rwhp.

TPC Intercooled SC:
- TPC info here.
- Approx 350 rwhp, flat torque curve.
- Price = $11.5k plus install, so approx. $14k total. DIY not feasible.

Protomotive Stage 1 bolt-on TT conversion:
- Protomotive info here and pricing here.
- Approx 350 rwhp, torque gain starts around 3300 rpm.
- Price - $12k plus $2k for no-cat option, plus install. Can be a DIY, so $14k total. The $12k system uses stock cats and no muffler, but for track use, running no cats with the $2k center-mounted muffler is best.

Engine Management Comparison:
TPC now uses an Eaton Gen4 roots s/c with 7th and 8th injectors and piggyback "UniQ" ECU. I'm not fond of this concept, but it does seem to work. Protomotive could reprogram the stock ECU to run a TPC setup, but the cost of that tuning plus larger injectors would offset the $1200 discount TPC gives for buying without the UniQ. But this path is not well travelled, so could get complex.
Protomotive reflashes your ECU (or writes you a chip) for their Stg 1 upgrade.

Reliability comparison:
TPC system looks pretty complicated, especially with the piggyback ECU. Its air-to-water intercooler requires an electric pump to pump water forward to a front-mounted radiator. I considered simplifying the system by using protomotive programming and an air-to-air intercooler, but ruled it out because (a) it would be pretty custom, and (b) unknown how well an air-to-air IC would work (not likely as efficient).
Protomotive system seems pretty simple. No electrical wiring needed; changes are mainly post-engine. Oiling is gravity drain back to custom lower valve covers.

Power & Drivability comparison:
TPC is the clear winner, with gobs of low-end torque. Reviewing a bunch of info, I came up with the following torque & power comparisons (at flywheel): (note: I downrated the TT kit a bit since my car is a '95)


The Protomotive conversion doesn't seem to give any real gains until 3300rpm+, which is a litte disappointing.

Heat/Efficiency comparison:
Turbos are the clear winners here. Whereas Proto's turbos (Garrett T3 Super60) run approx 65% to 75% efficiency across the rpm range and 6psi, a Roots SC will run around 55%. I was *very* disappointed to hear TPC's salesman try to convince me that turbos run inefficiently at 6psi. Come on. Look at the compressor curves. The fact is the air exiting the Roots SC will be 100F over ambient, while the turbo's air temp gain will be 75F to 85F. Plus, the 30hp used by the Roots SC contributes to power losses and even more heat. However, TPC seems to successfully manage all the heat with the A/W intercooler.

Conclusions:
- Both TPC and Protomotive Stg1 setups cost about the same. (Note- with either, you'll need some type of new rear wing. Can use RS wing with TPC, but need a turbo wing for Proto.)
- The additional torque with TPC's setup would be great for street driving.
- The complexity of the TPC setup gives me much pause for a track car. A water pump failure (for example) would be disastrous. The turbo setup is much simpler and the greater inherent efficiancy is appealing.
- The Stg 1 system can be later upgraded (thru engine mods) to get over 500hp, which could be nice.

One of these systems is going in my car this winter. Your thoughts appreciated!

FLYT993

Eric...damn! what a thoughtful and thorough analysis. I certainly don't have the knowledge and experience of 99% of most on this board....but from a logical standpoint, I like simplicity. It's a basic fact, the more complex, the more opportunities for something to go wrong (7th and 8th injector plus piggy back ECU). That fact alone would have me leaning towards Protomotive, since costs and power seem to be relatively on par.

Secondly, (and I don't know if there is truly any merit to it, it's conjecture) with all resources of $$, R&D, and engineering prowess, the factory has always chosen turbo power vs. supercharging. Why? There has to be a valid reason as to why they've always used the turbo...when they have the option to use whatever they wanted. Although RUF, now makes a SC, they built their reputation with the turbo, i.e., YellowBird. If immediate low end grunt is an absolute must then it's clear the SC has the advantage, but besides that single fact, what does the SC offer above and beyond a turbo?

The other thing that has always bothered me about "bolt-on" systems is I don't trust that you can simply "bolt-on" that much additional thrust and not modify the engine to cope. The standard 993TT had stronger connecting rods, pistons with lower crowns and coated skirts, plus the cylinder heads were deepened and strengthened and given thinner fins to help cooling....and the oil delivery system was upgraded (Total 911 Sept. 07).

You seem to be a deeply analytical type guy, some I'm sure once your analysis is complete, you'll have made the best decision for you. All the best....

WHB Porsche

I wouldn't be too worried about low-end power with a track car, as you can more easily stay in the power band. For street driving it's more of a concern.

I know you've probably considered it - but you can get a prepped TT track car for about $45k, such as ad# 7433 in the classifieds.

CornerCarver

Eric,
Great analysis. I did something very similiar back in 02 when I was considering both kits. At the time TPC kits were less expensive than Proto's turbo kits, because they didnt have the intercooler option. Now that both kits are priced comparably, the turbo kit seems to be a better bang for the buck. Protosport in Pomptain Plains, NJ installs the Protomotive turbo kits. I went for a ride in their stage 2 kit back in 02 and was very impressed with the performance. The great thing about the turbo kit is the ability to upgrade in the future. The TPC kit is capped off at around 6 psi. If my car didnt come with a TPC sc installed I would have strongly considered the turbo kit and still might, if I decide to remove SC and sell. It appears that you plan to keep your car for the long haul and you will eventually need to rebuild your motor, especially with 80% track time. It will be then when you will wish you went with the turbo kit as you can lower compression, strengthen internals and turn up the boost and you will be in an entire different league than my 5 psi TPC supercharger. Don't get me wrong, the TPC supercharger is phenominal for street driving because of the torque curve and holds it own against stock 993 TT's. It feels like a completely different car compared to my stock C4.
I am trying to get in contact with Automobile Associates in Connecticut. From what I've heard they have several customers tracking TPC supercharger kits. Does anyone track a proto turbo kit?

Bull

Eric, you have done all of the analysis, so I'll just relate the experiences of several track junkies whom I know with 993 conversions.

The TPC conversion was very difficult for one guy to get get running right, and keep running right. He finally gave the car to TPC and told them he didn't want it back until it ran correctly. Once it did, he had a leaking 7th injector problem, setting the car and the garage floor at Watkins Glen on fire.....both were quickly extinguished (I was parked next to him, but fortunatly was on track during the roast)! The car ran better for a while, then was totalled at Mosport (not related to TPC). He now loves his Turbo.

I know a few people who have had Protosport do the Turbo conversion, some Stage 1 and 2 kits. They have performed well on the track and to my knowledge the owners continue to be happy with the conversions.

YMMV, but I would do the Turbo conversion. Good luck with whatever you decide.

CornerCarver

"The Protomotive conversion doesn't seem to give any real gains until 3300rpm+, which is a litte disappointing. "

Do you really want any significant gains below 3300 for track application? Also, gives the car a chance to get moving so the tires dont spin for the entire first gear.. You are installing this in a C2, right?
I can visit Protosport to learn more about the kit, if you have any questions. Gives me an excuse to learn more about it.

Mark in Baltimore

What about a twin-engined 993? Anyone remember the Hubba Hubba Honda Honda that Car and Driver did back in the mid-'80's?

Seriously, Eric, neither choice sounds particularly appealing to me, but, then again, I know nothing of the Protomotive stuff. Since you have so much cash burning a hole in your pocket, why not come race in G class with us?

TheOtherEric

Thanks for all the comments so far. Especially you Bob -- I haven't heard about anyone tracking a souped up 993, so thanks. A leaking 7th injector ... Wow. Unfortunately, it seems there are so few Protomotive conversions that we won't know if it has its own problems.

You have a really good point there. Many corners at tracks around here are taken around 3500 rpm. I've been worried that the sudden surge in torque would make for a hectic corner. But OTOH, gobs of torque mid-corner might be bad too. No idea which would be better. Yes, it's a C2. But for sure, low end torque would be funner for street driving.

bv shady

Eric I am also on the fence with this decision. You will be doing it before I do so I am very interested in which one you choose. In my opinion it seems like proto is a better fit. They seem to have better knowledge /support than tpc and the nj location would make it easier logistically for me since I am in Pa. Al makes a good point it seems like you wil be keeping your car for the long haul and will eventually do a rebuild 500+ HP vs our now 282 and future410w/proto stage 1 will be very enticing at that time

TheOtherEric

That's what I'm kinda thinking too. The TPC would be funner for street driving (and can equal a 993tt!). But I hate complexity (hey, I'm an engineer) and reliability is a must.

Who knows, the TPC may be fine at the track, but for sure the risks are greater.

I'd love to, but it's not in the cards right now. I don't wanna turn this into a racecar, and buying a 2nd p-car isn't gonna happen for a while.

CornerCarver

[QUOTE=TheOtherEric;5006922]That's what I'm kinda thinking too. The TPC would be funner for street driving (and can equal a 993tt!). But I hate complexity (hey, I'm an engineer) and reliability is a must.

I think either kit will be a blast on the street and autox. The turbo is more suitable for the track as long as the fuel delivery is up to par and that monster intercooler runs efficient. Does the kit use similar piping as the 993 TT? I am wondering being that the turbos don't make boost until 3300 rpms that the piping might be inefficient and create too much turbo lag. This shouldn't be with the 2 small turbo's, but it just seems strange that they come alive so late in the rpm range. Have you discussed this with Protomotive?

"Who knows, the TPC may be fine at the track, but for sure the risks are greater."

As much as I want to believe this, I am skeptical. The kit was designed for safe street driving and autox's. I just can't see it running adequately for a 30 to 40 minute track session. I think the law of diminishing returns will present itself when driving hard.

Eric,
Does anything other than the torgue curve concern you with the Proto TT kit?
Have you driven a 993 with a TPC kit?

race911

Exactly. I think for a primarily track car, you'll find much more to be gained by taking the suspension to the next level. (Now I'm sure this more power want is driven by long straights by the tracks you normally run.) I think it's false economy to bolt on ANY of these forced induction systems to a stock engine, anyway.

Another point on my data will be a week from Tuesday when I'll finally run the yellow car at Laguna. If, as I suspect, the 3.8 isn't worth a whole lot, my mind will pretty much be made up just to drop one of the stock 3.6's I've got laying around until I decide if a PROPER turbo engine is in the car's future.

One name I'll drop that I'm not sure I've really heard mentioned around here, and he's got a LOT of race cars nicely built out our way, is Matt Lowrance out of Reno. He used to race IMSA as a privateer, and over the years he's run some pretty impressive single turbo racers based on old torsion bar chassis. I'm sure you can find race results at the club racing website or mylaps. I know he's gone over to a n/a 4.0 engine lately. But his old turbo car would run even with Bob Stefanowicz's cost-no-object Jerry Woods built cars, say 1:30 at Laguna, 1:50 at Thunderhill. So there's an option for someone who's got proven results, and isn't a bank breaker.

revolution993

I am looking to upgrade to a TPC kit also let me know your decision and what you think about it.

RallyJon

That makes no sense at all. 3.6L and 11:1 compression with turbos sized to make 6-8psi, should have you making full boost and serious torque by 2200-2500 rpm. T3 Super 60 may be too large for a low boost twin turbo. Or maybe their plumbing is just that inefficient and restrictive?

With aftermarket turbo systems, making the piping short and smooth is everything for driveability. A car that makes no boost until 3300 rpm would be a nightmare to drive--like some old 70s 930. Isn't the T3 like >10 years old by now, too? Not ball bearing, so that's a few hundred more rpm to wait for boost.

For comparison, my old hacked together Subaru RS (2.5L, 10:1 compression) had about $1000 in parts: a used T3 Super 70 from the rally car, some old pipes from a Saab turbo, a Midas-quality custom exhaust and a used intercooler. Made 5psi by 2000 rpm and pulled as hard as my STI. Ran it for 25k miles and several track days, including one that was 95 degrees in the shade.

CornerCarver

I couldn't agree with you more. This kit is at least 6 years old and more efficient turbos would probably help. If those torque stats are true then the plumbing is inefficient. What are we missing here?