911, 911 Porsche, engine builder, Forced induction, porsche performance, Projects, turbo Porsche, Uncategorized

3.4 Twin plug 930 Engine build and tranny rebuild

This was a pretty good example of a 86 930. Black with Fiske wheels, boxed rockers and a few goodies in the suspension already in place. The car even supported the Ruf green interior which I love since it is off the beaten path. The motor however had some work that it needed. With a very high leak down we started snooping around as to the cause of the damage. Anytime we see a boost controller and fuel enrichment systems you have to wonder how much was enough with the previous owner. So many times that rush of boost is addictive and the knob gets cranked until damage occurs. In this case that is exactly what happened. When we opened the motor we found pitted heads and damage to the piston and cylinders.

 We quickly started our journey to rebuild by powder coating all the tin, sending the heads out to be welded up, twin plugged and cleaned and a little of our magic applied, then ordered up a set of Mahle 3.4 liter, 7:5:1 CR pistons and cylinders. We took the numbers from the heads and then built a set of cams to take advantage of the flow. While the machine work was being performed we assembled the lower end. This process takes time because not only do we put the motor together once we do it twice. The first time we put everything together but not in final form. We do this to take it back apart and check all of our spec with the new bearings and parts. This is what is often referred to as blueprinting. We make any adjustments needed and reassemble the motor hopefully for the final time. Sometimes this process can take several times to get right where you want it.  Included in that process is the upgrading of the rod bolts and the head studs to a stronger version to cope with the new found HP.

 The car was then fitted with a crank fire wasted spark ignition system. The point of the twin plug is to create a more efficient burn in the chamber thus allowing less timing and creating the same effect without added stress to the motor. The system is digital and uses a sensor and teeth to read instead of a brass gear on the crank that wears in time. The digital system keeps its timing within a 10th of a degree. We do this anytime we add a higher compression ratio to cope with today’s octane and quality of gas. Keeping in mind that newer cars do it with EFI and knock sensors. We have to do it the old fashion way. To farther the safety of the motor we also modify the CIS fuel head to supply additional fuel where needed.

 We then move to the external parts to create HP. Short tube headers do not only remove unwanted weight but also over 4 ft pf pipe. The faster exhaust gets to the turbo the faster it can build boost. With the added CR and displacement the turbo will move that much faster through the short tube headers. On the end of that run the turbo is upgraded with one of our K27S turbos. This turbo is designed specifically with our builds in mind. The inlet is enlarged to a 3 inch opening with a venturi to increase velocity across the inlet of the turbo. With our own compressor housings the AR is kept tight therefore increasing efficiency of the turbo. The end result is a car that makes more power under the curve and drives like a NA Carrera car until boost kicks in. When does that boost happen? Well, the factory setup makes it full boost around 4-4300RPM. Our signature build will move that power band to apx 2800RPM! To compare the two is not even fair.

 This build was first developed many years ago on my own daily drivers and it in my wife’s 930 cab. These builds are some of our favorites and for the people that don’t have a 40K budget you get big results and big HP even by today’s standard. Vertigo…well we can’t tell you what it feels like but we can built it. This build will make apx 450-475HP.

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