996 C4 with Twin Turbos added
Discussion
I wouldn't do this - adding Twin Turbos to anything will cause headaches along the line. Are they fiddling with the pistons and con rods for your 8k-10k? I doubt it. That would mean about 0.6 bar boost, so you'd probably get about 400 bhp out of it comfortably. I wouldn't go much higher than this, otherwise clutch, driveshafts etc may start to be at risk. I'm sure the Turbo will have had these uprated for its specification.
To be honest, the best route would be to add a low pressure supercharger if possible, an easy fit for about 5k to the 964/993 engine, but I'm not sure about the water cooled 996. Because you only need low boost, this makes most sense. Twin turbos are needed for high boost applications of 1bar and over, as they can shift a lot of air using a small turbine (minimal lag). Using a single low lag turbo would give inefficient air flow, and a big turbo would take too long to spool up.
If you wanted a real monster, yes, get twin turbos, but get a specialist to do the whole thing, making sure pistons, conrods, crank, injectors etc are all matched to the new spec - plus the brakes, clutch and driveshafts can take it. RUF do it best, at more than 8k-10k I hasten to add ;-)
Conclusion: stick with 300 bhp (it ain't a slow car!) or enquire about supercharging. Or flog the car and get a 996 Turbo (LHD these are down to 60 odd grand now).
Rgds
Domster
To be honest, the best route would be to add a low pressure supercharger if possible, an easy fit for about 5k to the 964/993 engine, but I'm not sure about the water cooled 996. Because you only need low boost, this makes most sense. Twin turbos are needed for high boost applications of 1bar and over, as they can shift a lot of air using a small turbine (minimal lag). Using a single low lag turbo would give inefficient air flow, and a big turbo would take too long to spool up.
If you wanted a real monster, yes, get twin turbos, but get a specialist to do the whole thing, making sure pistons, conrods, crank, injectors etc are all matched to the new spec - plus the brakes, clutch and driveshafts can take it. RUF do it best, at more than 8k-10k I hasten to add ;-)
Conclusion: stick with 300 bhp (it ain't a slow car!) or enquire about supercharging. Or flog the car and get a 996 Turbo (LHD these are down to 60 odd grand now).
Rgds
Domster
I did find a 993 C4 that had retrospective twin turbos fitted by German tuner Lotec, but as I said before, I'm not sure the complication and expense will be worth it. The Lotec conversion makes 450 bhp, but I'm not sure what they do or how reliable it is.
The reason Porsche only push 420 bhp from their twin turbo engines (when they are tuneable to over 600 bhp!) is mainly for reliability purposes, and also because conversion costs get exponential the higher up the power curve you go. For example, in your car, standard injectors would probably cope with a 400 bhp set up, but at 420 bhp they would be running flat out (not recommended) and you would need to upgrade them... possibly making other changes to the fuel system (regulator, pump) along the way.
Although 600 bhp may seem attractive to some owners, you would realistically have to service the car every 3000 miles and rebuild the engine once a year. This would guarantee a card from your local Porsche dealer... and your bank manager!!!
FYI, I once had a tussle with a 996 in my Lotus Carlton, and he seemed every bit as rapid. Maybe ask Autofarm or AmD if they know of any sensible mods to liberate a few more bhp, like a free-er flowing exhaust, sports cat, improved air filter and chip. Together they may make another 30 bhp, at a cost of maybe a couple of grand.
Rgds
Domster
PS If you are dead set on supercharging etc. then try Autofarm in Oxford, as they know about Eaton superchargers for the 964 engine, and maybe other applications.
Edited by domster on Thursday 20th December 09:46
The reason Porsche only push 420 bhp from their twin turbo engines (when they are tuneable to over 600 bhp!) is mainly for reliability purposes, and also because conversion costs get exponential the higher up the power curve you go. For example, in your car, standard injectors would probably cope with a 400 bhp set up, but at 420 bhp they would be running flat out (not recommended) and you would need to upgrade them... possibly making other changes to the fuel system (regulator, pump) along the way.
Although 600 bhp may seem attractive to some owners, you would realistically have to service the car every 3000 miles and rebuild the engine once a year. This would guarantee a card from your local Porsche dealer... and your bank manager!!!
FYI, I once had a tussle with a 996 in my Lotus Carlton, and he seemed every bit as rapid. Maybe ask Autofarm or AmD if they know of any sensible mods to liberate a few more bhp, like a free-er flowing exhaust, sports cat, improved air filter and chip. Together they may make another 30 bhp, at a cost of maybe a couple of grand.
Rgds
Domster
PS If you are dead set on supercharging etc. then try Autofarm in Oxford, as they know about Eaton superchargers for the 964 engine, and maybe other applications.
Edited by domster on Thursday 20th December 09:46
My 993 C4 has had a few AMD mods (at the hands of a previous owner)to the engine management, filter, exhaust etc. 315bhp/6100 and 287lbsft/5000rpm so healthy gains. Receipts for about £1500 and the quality of the work is impressive. I wouldn't go down the route of massively modding a 911 of any persuasion, my father had a 993 turbo reliably pushing out about 650bhp but engine conversion costs were £28k before you even start on brakes,suspension etc. (about 50k all in. I'll get dad to publish details if anyone's interested). Adding twin turbos to a 996 C4 is asking for trouble/expense, but if you must do this Autofarm are the people to speak to.
Domster, you're the last person on here I want to get into the usual "my car's better than your car" debate with but:
"FYI, I once had a tussle with a 996 in my Lotus Carlton, and he seemed every bit as rapid. "
I should blooming well hope so! Lotus Carlton 0-60 5.3s 0-100 10.9 top speed 173mph. Porsche 996 C4 0-60 4.9 0-100 11.7 top speed 174mph (figs. from Autocar). The Carlton is quicker at massive speed and through the gears owing to the epic torque, but a standard 993 should hold its own in a straight drag race...
Edited by jaydee on Thursday 20th December 10:35
Domster, you're the last person on here I want to get into the usual "my car's better than your car" debate with but:
"FYI, I once had a tussle with a 996 in my Lotus Carlton, and he seemed every bit as rapid. "
I should blooming well hope so! Lotus Carlton 0-60 5.3s 0-100 10.9 top speed 173mph. Porsche 996 C4 0-60 4.9 0-100 11.7 top speed 174mph (figs. from Autocar). The Carlton is quicker at massive speed and through the gears owing to the epic torque, but a standard 993 should hold its own in a straight drag race...
Edited by jaydee on Thursday 20th December 10:35
I wouldn't get into a bunfight with you Jaydee, especially as I may need your help in getting your dad's 968CS at a good price ;-))
Yeah, figures for the 996 are virtually identical, although someone once got the Lotus to launch to 60 in 4.8.
However, it was the in-gear stuff that impressed me - the LC does 30-70 in 3.8 and that was the main 'drag' I had against the 996.
As you say, at silly speeds the weight of the LC is less of an issue and torque takes over. Not much lives with a 0-140 time of 21 seconds.
I am always impressed how much performance 911s have for their horsepower.
Rgds
Domster
Yeah, figures for the 996 are virtually identical, although someone once got the Lotus to launch to 60 in 4.8.
However, it was the in-gear stuff that impressed me - the LC does 30-70 in 3.8 and that was the main 'drag' I had against the 996.
As you say, at silly speeds the weight of the LC is less of an issue and torque takes over. Not much lives with a 0-140 time of 21 seconds.
I am always impressed how much performance 911s have for their horsepower.
Rgds
Domster
Are you really sure you want to sell this car ??? 
Hi domster,
Sorry to bother you at work. I've passed on the address and dad's going to send you the specs and some jpegs anon.
Jarel Dokic
ps: also sorry for confusion
I could tell you were having a "who the hell is..." moment 
Too much
and not enough 
for me to manage coherent speaking/thinking/gassing this morning...
Edited by jaydee on Thursday 20th December 11:51
Sorry to bother you at work. I've passed on the address and dad's going to send you the specs and some jpegs anon.
Jarel Dokic
ps: also sorry for confusion
I could tell you were having a "who the hell is..." moment Too much
and not enough for me to manage coherent speaking/thinking/gassing this morning... Edited by jaydee on Thursday 20th December 11:51
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