Jussi

I've been reading this forum with a will and am very grateful to those who share their knowledges and informations, like Jean, Edpurplett, MOD, TB, Red etc (too many to list).

First I combined and scaled the most common dyno charts in this forum:

Because I'm searching engine tuning parts for street usage with good mid range torques, I'll choose the way like MOD500.

The one big question here has been between Single plug and Twin plug system. Twin plug system is much more expensive but is it worth the effort?
The next comparison between two almost similar tunings: RS spec cams, K24RS turbos, Cargraphic's mufflers&cats etc. - only difference is Single/Twin plug issue..

from this picture, it can be noticed that Single plug version(blue color) is good enough against Twin plug version(black curves)!
The red curve is from original 993TT. MOD's car is very considerable in every way even compared to this original at low RPMs..

So my conclusion from these cases,
(if the target is about 520hp/700Nm, money matters and the car will be used mostly in street, )
are following:
- Carrillo rods
- Flame rings
- Flowed and ported cylinder heads
- Sport camshafts, RS specs (hydraulic)
- 5 bar FPR
- upgraded oil cooler system
- K24RS turbos
- Cargraphic mufflers/cats
- ECU tuned with these in dyno
Does anybody shares my opinion? Or absolutely disagree with something?
Let's talk

Rassel

Isn't MOD using Kevins hybrids, while Toby is using K24/K26 Alzen Turbos?

Edit: I what is Jeans car doing on the graph? It looks like it would be of the scale on the second dyno pic

Woodster

Js: Great basis for discussion.
I will defer to the experts for their comments.
where are you located?? Are you willing to have your engine
built in a different country?
Marty K

Kevin

With all things being equal.. Two seperate engines built the same way, with one being twin plug, and the other single plug.. There is a greater safety margin from detonation. When you twin-plug your engine you build in a safety factor. You can also allow more timing for more power, which will be far less than the maximum timing that you ran in the single plug version. If 520 was your limit, why install flame rings.. Flame rings are a safety net.. Why install Carrillo rods?? The engine isn't at 550??

The way that I look at it is, labor to rebuild these engines is high vs a Supra engine or Chevy V8.. Gasket set are expensive.. Why risk it.. The other point is, once knock is detected, power is reduced.. It is night and day at over 500HP.. If one runs back to back dyno runs and you heat up the intercooler charge air, you will see the power dropping as you lengthen the run time in the single plug engine. In the real world this relates to people saying, damn my car is fast on the street but when I am on the track, the car feels sluggish..

JJayB

[QUOTE=Kevin]With all things being equal.. Two seperate engines built the same way, with one being twin plug, and the other single plug.. There is a greater safety margin from detonation. When you twin-plug your engine you build in a safety factor.

Kevin is right on. The factory race department figured this out 10 yrs ago.
When you split the case whats a few bucks more to build in reliability, unless you just do dyno pulls. Btw, the twin plug dyno runs resulted in over 30 lbs ft of torque over a single plug motor. For those who track your cars you know this results in quicker acceleration out of the corners. Dyno runs are a little misleading with all the emphsis on HP. Thst why I like the 60-130 mph thread its real world.

Rob 97 993c2

excuse my ignorance, but why didnt porsche make the 993tt engine a twin plug when the 993NA engine is a twin plug? Would it have been that much more expensive or difficult? How about a 964T motor - is that twin plug?

JJayB

Never under estimate the power of bean counters even in a company like Porsche. Another issue is why didn't they use bronze valve guides rather than the junk ones in the turbo. $$$$. Remember they only had to tune for 400-450 hp. Rennlist didn't exsist back then so how did they know that we wanted 600 trouble free horsepower. Emissions, noise and OBD where bigger concerns. The develpment budget sometimes gets in the way of what seems to be logical. The last generation of the GT2 race cars I believe were twin plugged which was needed against the Viper GTRs.

Jussi

MOD wrote:
"The K24 RS ZC turbos themselves are very interesting, they are K24 RS units that have been rebuilt by Kevin, and feature his ZC technology and other modifications."
Maybe this Kevin's ZC rebuild makes a big difference. Torque values below 3500 rpms are about 50 Nm better

Jussi

If the car has driven 125k miles and performance tuning is in mind.. Engine must rebuild anyway. All new bearings&gaskets, Pistons and Cylinders must be changed. Carrillo rods are about same than original Rods. Flame rings cost just $600 more. These are quite cheap insurances like also $500 ARP head studs.
When going to twin plugs, it cost many thousands (>$4000?) more. I understand that this will increase safety factor again but if car's mainly purpose is street usage and just few quarter mile runs per year is driven..

Steve Weiner-Rennsport Systems

"Brother" Kevin:

A clarification is needed on the subject of twin-ignition,...

Using two, simultaneously firing spark plugs in these engines REDUCES the need for ignition advance required for full power. In effect, the engine does less "negative work" since the sparks can be timed closer to TDC for a greater "push" at, and beyond the point of ignition.

One sees this clearly on the dyno on all 911 motors where a single-plug motor needs anywhere from 33-36 degrees total for maximum performance. Twin-plug motors detonate like crazy with that timing and instead, prefer total advance in the 24-27 degree range (depending on bore size, piston dome shape, & static compression) to achieve peak HP.

Concluding;....Twin-plug motors want LESS, not more timing (everywhere in the RPM range) than single-plug motors,....

Without question, adding twin-ignition reduces these engine's appetite for octane (to a point) and provides that safety margin against detoantion. Its good insurance if one can afford it and further, twin-plug motors have sharper mid-range throttle response and will make more mid-range torque; all things being equal.

Just my 2 cents, of course.

Miles965uk

What is the cost breakdown on this twin plug setup?, I thought it was just machine head work and you only need to add additional coil pack which isnt expensive - unless you mean using the porsche twin distributor but then that isnt any better vs a coil pack?

Jussi

Only price information I have is from Andial:
"Twin Ignition Components" - includes signal splitter, dist, modifying misc sheetmetal and heater channel.
Price $3900 and that is not included head works..or isn't?
quite expensive insurance..
Or is there cheaper way to do it, like from RSR parts?

Kevin

Steve the numbers for the twin turbo are a little different than a NA 993 engine. When you run lets say 91 octane a 1bar boost with my Stage 2 Z/C turbochargers, the knock counts increase from 22-24 degrees.. However, peak torque is at 28 degrees (with all conditions being perfect).. However, knock is raising it's ugly head.. The end result is timing being pulled (less torque, less power). If one runs higher octane, more timing can be achieved to try to obtain the peak torque number.. Or with the twin plug 993 Motronic turbo engine one can run higher boost levels and timing levels with lower grades of fuel (realize that your not near the peak torque number). Or one can run timing close to peak torque number, with lower knock counts, with higher margins of safety, which yields maximum torque..

TB993tt

The comparison of my 522hp K24RS turbo TS motor with MODS single spark is not quite as straight forward as it seems.

MODs motor has the latest 127mm race cats (only available in last 2 years) together with big piping and race C/G mufflers. My 522 motor had smaller 100cell cats and piping and "sport" C/G mufflers - this set up makes a big difference at the top end
Also my 522hp engine was dynoed with the TTP/FVD/CG intercooler which is worse than stock.


The RS dyno does not show the benefit of the TS - in on road driving it is all about the overboost on these RS engines - this is what makes them so fast. Punching the throttle at 4K rpm can result in as much as 1.5bar in my motor, I am guessing that MODs will not overboost quite as much as this - the difference between MODs and My overboost levels will be 90% attributable to the TS. On the road the 1.X bar overboost is BIG torque.
As far as the relative drivability and responsiveness, we will be able to report on this in the future.
The problem with TS is getting the Motronic to work with it - Ruf gave up, I think Andial ended up with a generic RS program.

Rickard 993 Turbo

Why talk about 91 oct fuel, i can't understand people that not run the best pump fuel avaibly