DV 993tt

First, some details about my car. My '96 993tt has the FVD 525Bhp kit. This includes a sport motronic, powerflow intake, 5 bar fuel pressure regulator, oil cooler, modified K24s, cams, and mechanical rockers. In addition I have 102mm P&Cs, Carillo rods, diverter valves, cat bypasses, and muffler bypasses. My car is also light with no sunroof, GT3 seats, RS door panels, no trunk carpet, no spare, and no rear seats. I would guess my car is 150lbs lighter than a "normally" equipped 993tt. This setup feels like a really strong normally aspirated engine below 4000rpm and after that all hell breaks loose all the way to redline. This car is fast! I've timed myself going from 100-200kph at about 8.5 seconds.

I sent Kevin my stock k16 turbos last month and we decided stage 4 would be appropriate for my car.

I spent most of Saturday installing Kevin's stage 4 K16s following his detailed install procedure. Then I spent a couple of hours Saturday night running in the "new" turbos again following Kevin's specific instructions.

Sunday morning, I went out and continued running in the turbos. After about an hour, I started giving the engine some boost. Disappointment! The car felt slower than before! There were also some strange vibrations going on and it got worse the more I drove. It felt like I was missing a cylinder or two. I call Kevin and we disscussed some possible problems.

So this morning I decided to first change the spark plugs. Problem solved! The engine is again smooth and steady.

I go out for a test drive. After warming up I mash the pedal and all hell breaks loose!!! All hell breaks loose NOW!!! Not after 4000 or 3000 but NOW! Warp speed NOW!!! Everthing is a blur! No lag!!! NONE!!! All the way to redline which comes too fast!!! I can't shift fast enough! Tires breaking loose every time I shift! Simply amazing how much faster an already very fast car can get with Kevin turbos. Incredible!!! Kevin's magic is just amazing. Thank you Kevin for such an awesome product!

Kevin's little k16 flow much much more than even the modified k24s I had! No comparison! David just killed Goliath!

One problem though, the intercooler hose popped off during just the second full throttle run. This gave me quite a scare. I hear a loud pop and the engine went dead. After checking everything, I connected the hose and went on. Does anyone have any experience with the intercooler hose popping off? What's your solution?

JW
'96 993tt 3.8 Zero Clearance
'92 968 race
'89 944 turbo 3.0 race
'86 930

Geoffrey

You may want to get t-bolt clamps for the intercooler hoses, they grip much better than stock stuff. You can get them from any performance turbo house like Turbonetics.

A couple of other things to consider. The stock 44lb/hr injectors are small for what you are asking them to do, and driving them at 5bar fuel pressure rather than 3.8bar only gives you a minimal return. I would check out your air fuel ratios before beating the car too much. I can tell you from experience that 12.7:1 afr is too lean on an enduracne racing engine (meltdown). I realize that street applications are different, but I'd still like to see 12.2:1 afr on your car while under boost. You will most likely need your ECU reprogrammed.

DV 993tt

Geoffrey

Thanks for the recommendation. What injectors did you install in the 650hp 993tt you mentioned in another thread? Do you have a supplier name and part number?

Thanks

JW
'96 993tt 3.8 Zero Clearance
'92 968 race
'89 944 turbo 3.0 race
'86 930

hatchy

Are you going to have your ECU reprogrammed for Kevin's K16s?

Geoffrey

Turbonetics has them as do most performance turbo supply houses. Hoses poping off are not uncommon with turbos that flow more air. I have found that 3.3-3.8l Porsche engines at stock fuel pressure 3.8bar 55lb/hr injectors are good for 550-575hp where they hit 85% duty cycle. I installed 72lb/hr injectors in the 993tt I referenced above although 55lb/hr ones would work for his application.

Herein lies the issue with stock ECU remapping. The stock injectors are saturated injectors (high impedence, low current). The larger the injector, the larger the coil required to open the injector. Generally speaking, saturated injectors tend to be smaller injectors. The larger injectors are peak and hold injectors (low impedence, high current). Beyond about 50lb/he injectors, with few exceptions, they are all peak and hold injectors. The Bosch ECU injector driver component was designed for low current (saturated) injectors and will burn out if peak and hold injectors are used. There is a physical limit to the amount of flow a 993tt injector can provide regardless of the fuel pressure used. Increasing the fuel pressure gives a diminishing return, as the fuel pressure goes up, the less and less of an increase of fuel is provided.

I think there may be some companies out there (RC Engineering) that produce custom injectors, but you'd need to work with someone who can remap your entire ECU if you change injectors.

DV 993tt

No. I want to see how well my FVD 525hp ecu works. If I am not satisfied with the FVD ecu, I'm going Motec.

JW
'96 993tt 3.8 Zero Clearance
'92 968 race
'89 944 turbo 3.0 race
'86 930

DV 993tt

Geoffrey
Is there a simple solution where I just install different injectors? How about the 72lb. injectors you used in that 650hp car? Was there special programing to accomidate the 72lb injectors?
Is there another way? How about additional injectors?

JW
'96 993tt 3.8 Zero Clearance
'92 968 race
'89 944 turbo 3.0 race
'86 930

TB993tt

DV993tt
Not questioning your butt dyno or anything but any chance of a chassis dyno run ?

Geoffrey

I am not an expert on factory type ECUs specifically and have no access to the programming code. I install and program only aftermarket ECUs and the car had MoTeC, so I just told the ECU that it had low impedence injectors and programmed the fuel tables for the larger injectors and it was fine. I also haven't played with additional injectors since the 1980s when laptop progammable systems were not available but I want only 1 system in the car, not 2 competing systems, so I don't like it. It may work, or you may have a partial solution, or you may beat your head for months.

Kevin

John;

Thanks for taking the time to trouble shoot the plugs!!! We do need to check the AFR's ... !!!

By the way you are the prime canidate for Motec! WITH Traction control, and Geoffrey is the man to put this project all together!!

DV 993tt

Kevin
I am going out of town for a week. I will check the AFR when I come back next week. I am sure the car is runnung lean though.
John

hatchy

Would P&H injectors + resistor box work on the Motronic ECU? On another car, I've done this (270cc saturated to 550cc P&H) and it worked fine. Are the injectors onthe 993TT ~12-15 Ohm or is it the funky 5 Ohm Bosch?

Geoffrey

The 993tt injectors are 12ohm injectors. The low impedence injectors really need the current to open them, that is why they are peak and hold. By using resistors you really aren't getting the current, and therefore the performance from the injectors that you need. They become slow, sloppy, and inconsistent.

Jeff 993TT

Ugh.. Now you tell me about this..

nman413

Jeff, time for you to get Sam's turbo and start the process all over again