911 sc 3.6 to 3.8 engine rebuild thread

[targa72e]

Here is my 964 for comparison, dynoed on the same dyno (at DynoPro Denver). Engine is rebuilt 3.6, mostly stock internals with the exception of ARP rod bolts and DC 993 SS cams. I have a single pully fan conversion, light weight flywheel and a FVD exhaust with 200 cell cats and standard Steve Wong chip. I am also a little lean as well and should probably have a custom chip made. Looks like you make better power at the top end and better torque below 4500rpm.




john

[-Levi-]

Originally Posted by targa72e

Here is my 964 for comparison, dynoed on the same dyno (at DynoPro Denver). Engine is rebuilt 3.6, mostly stock internals with the exception of ARP rod bolts and DC 993 SS cams. I have a single pully fan conversion, light weight flywheel and a FVD exhaust with 200 cell cats and standard Steve Wong chip. I am also a little lean as well and should probably have a custom chip made. Looks like you make better power at the top end and better torque below 4500rpm.




john

John, thanks for sharing, great info from the same dyno.
What did your AFRs look like?

[targa72e]

Here is the A/F graph from the dyno run. You can see I could use a little more fuel in most areas.



john

[MoreGAS]

John -that is really quite lean and you could make a fair bit more power and reduce detonation risk(especially where most lean at Pk Tqe which is totally undesirable and backwards ) by adding an adjustable fuel pressure regulator and raising the pressure without needing another custom chip that kind of missed the mark Rd 1 . You will end up a bit "soggy" (lose power) at 6K where you are the richest now 12.5:1 but I suspect you are not there that often on a streeter.

You have to double quadruple the pressure to double the flow roughly, so there are limits here.
Search the net for the formula and if you cannot find it PM and I will give it to you .

beST
Kevin
GAS Motorsport

[JoeMag]

Levi -- Regarding Kevin's comments above to John, you're going to need to get more fuel to your motor too... Running at over 14 across the RPM range, and then just under when you w went to silent mode is way too lean.

It's a stout motor you've built. I wouldn't think going up to 7k would be an issue. ...btw, is the crank cross drilled?

[winders]

I'd be looking in the .85 to .88 Lambda range....It's better to be a little rich than too lean.

Why do you guys use AFR????

Using the standard AFR for gasoline (which varies, by the way):

14.7 x .85 = 12.495
14.7 x .88 = 12.936

[-Levi-]

Originally Posted by JoeMag

Levi -- Regarding Kevin's comments above to John, you're going to need to get more fuel to your motor too... Running at over 14 across the RPM range, and then just under when you w went to silent mode is way too lean.

It's a stout motor you've built. I wouldn't think going up to 7k would be an issue. ...btw, is the crank cross drilled?

Thank you,
Crank should be stock, I do not believe we modified that. the plan at this point is to go up to factory redline for the 95 engine (6800) I assume I will be more than safe there.

Agree, sent an inquiry to Steve Wong about making adjustments to the setup.

[-Levi-]

Originally Posted by winders

I'd be looking in the .85 to .88 Lambda range....It's better to be a little rich than too lean.

Why do you guys use AFR????

Using the standard AFR for gasoline (which varies, by the way):

14.7 x .85 = 12.495
14.7 x .88 = 12.936

Speaking only for myself, I have a very basic understanding of tuning. I'm using AFR as it was available from the Dyno and from my Wideband I run on the car, its also related to the first line.

[Bill Verburg]

993 injectors may be running near or at 100% duty cycle w/ the combo of 3.8 + ethanol gas

The 993 has early generation, no longer used, "EV1" pintle orifice fuel injectors and I wondered if they could be changed to the later "EV6" 4 hole, spray screen orifice injectors. EV6 injectors are resistant to ethanol and are supposed to provide better atomization, lower emissions and less sensitivity to fuel pressure.



the stock 993 fuel injector has the following specs:
Bosch number 0 280 150 786 is at 15.6 ohm, 234 cc/minute, 22 lb/hour at 3 bar.

Bosch Motorsport has an injector with almost identical specs (maybe another with closer specs?):
Bosch number 0 280 155 931 is at 12 ohms, 273 cc/minute, 25 pounds/hour at 3 bar.

The Motorsport injector appears to be an interchangeable size and connector for the 993 injector.

the stock 993 injectors run near 100% duty cycle w/ @ 6800 + 3.8 + ethanol gas near sea level

[-Levi-]

Is this what you are referring to?
https://patrickmotorsports.com/products/fue99360612000hppms?_pos=1&_sid=ac0f2743a&_ss=r

I’ve also heard 944 turbo injectors may work.?.

I would like to figure out if I need these before spending the money. Hopefully I can connect with Steve Wong to hear his input.

Thanks the the help Bill/ everyone

[targa72e]

As Levi indicated A/F is just the default from the Dyno shop. With the run file it can be changed to Lambda, still indicates the same thing, need more fuel.



As far as injector size, keep in mind we are in Denver. Because of our altitude we only have 80% of the air (and fuel) going into the engine as you would at sea level.

My chip is currently the base upgrade for stock engine with light weight flywheel. Since I have added headers and cams (which bumped my HP quite a bit) I probably need to get a new chip that better matches the engine. Steve offers custom programmed chips tunned to your engine.

john

[winders]

Originally Posted by targa72e

As far as injector size, keep in mind we are in Denver. Because of our altitude we only have 80% of the air (and fuel) going into the engine as you would at sea level.

Sure. But, you need to make sure you have enough headroom to properly fuel the engine at sea level. After all, you might actually temporarily leave the Colorado Plateau for some reason.

[flat6pilot]

Originally Posted by winders

I'd be looking in the .85 to .88 Lambda range....It's better to be a little rich than too lean.

Why do you guys use AFR????

Using the standard AFR for gasoline (which varies, by the way):

14.7 x .85 = 12.495
14.7 x .88 = 12.936

I'll agree with Scott especially if you're just getting into tuning, get familiar with the Lambda scale. (more accurate representation) It can also be used universally to read all types of fuel like gas/diesel/methanol,E85 etc... as AFR scales are different for each type of fuel. Most newer gauges are capable of displaying AFR or Lambda.

However, nothing wrong using AFR if you only use one type of fuel and that's what you're already used to.

[PeteKz]

Agree with Scott. Lambda is what the O2 sensor actually reads. The display converts that to AFR via a simple table with the assumption that Lamba 1.0=14.7 AFR. 10% ethanol contaminated gas actually has a stoichiometric AFR of about 14.1, not 14.7, but the "AFR display" will show 14.7 when lambda=1.0 and burning 10% ethanol crap.

According to Bosch, max power is around lambda=0.90, however, 0.85 gives up almost no power, and increases resistance to detonation, so .85 is safer for most purposes.

[MoreGAS]

Levi
A few thoughts given this was your thread ; your engine is even leaner than John's running 14-14.5:1 AF nearly the entire run. While engines can make peak power at a pretty wide range of AF (or lambda -better to think in lambda as lambda 1.0 IS the same no matter what your fuel) ) , we use the extra fuel to thermally manage this combustion w our goal to make maximum power RELIABLY, this hurts economy(efficiency) and emisions a bit, but that most likely is not you goal when you bought all those Hot rod engine components.

The power (which is corrected SAE J1349 std look it up-you lose 19% according to this spec vs sea level-crazy high-get a turbo lol!) is not what I would expect given your engine's set up. We use a Dynojet in various clubs for Clubracing to set hp/Wt classes and police it , and readings repeat fairly reliably corrected back to this std at sea level, atleast below 3K ft where we race in my experiences(dyno goes to various tracks) . I suspect power levels will get better if you run it at say -.85 - .87 lmbda at PK tqe and a little leaner near pk HP- say .88-.90. Start rich, (with better injectors more modern ev6 style w higher flow 4 hole nozzle -flow tested matched sets we can provide) ) this is where an adjustable FPR helps. You can lean out slowly to a safe level. It will run hard much more safely there at those lambdas. Don't disable you knock sensors, it is hard to know whether your knock sensors are functioning correctly, without making them knock w poor fuel and or alot of ignition advance for a brief period high load but low risk say full throttle 3500 -3750 RPM. You unfortunately don't have this tuning flexibility w a stock ECU(vs programmable stand alone w often go to) unless someone is there live w tuning tools to try these tests live . You can however, make sure the engine is pretty warm so go easy on the cooling fans, get oil temp to say 200-220 F but know if air temp gets high, the ecu will pull out a bunch of timing , so a little air blowing on intake mass air sensor area is ok. If you see random runs where after several pulls and a little sitting the power will all of a sudden be quite off, like 15+-hp and tqe, it either has quite high head temps and is knocking, or high air temp, both pull out loads of ignition timing in your ecu and all stock Bosch ecus as a protection strategy.I read 6 degrees fist time it senses knock, then pulls out 6 more if not done knocking next cycle, that is tremendous, demonstrating how once it starts, detonation takes drastic measures to stop. You want that safety, at 11.4:1 as in my book that is too high of compression for street fuel . Know an "11.3:1" 964 when CC'd out is actually 10.4 ish by Porsche. So ignition your timing has to be conservative, especially if you cannot verify your knock sensors are working properly.
Check that your throttle is going 100 pct full as I recall once n a V ram clients car , they attached the created linkage in the transplant to a connection point(maybe cruise control) where it went only about 80% throttle and the power was way off, A/F ratio or lambda curve was also. Your fuel curve looks alright, but worth checking. Also make sure the system goes in to WOT mode on the Reso flap(s) in condition 3 shown prior(I didn't verify that posts info) , and that you have the big multi balled reservoir vacuum chamber these come with so it can actuate all these V ram valves repeatedly and correctly. Maybe watch those vacuum actuated levers on a pull or put a Go pro there is too scary to have your face there(been there lol) . WE watch ign timing this way w a light on the crankshaft if we suspect timing is being pulled out from knock(watch your hoodie strings or T shirt don't get sucked in to the fan-not lol done that) Perspective- Typically w good headers and exhaust, on a stock" 993 3.6, and good fuel, we can get out what Porsche rates these flywheel at the wheels. This would be 270-275 wheel hp on a dynojet SAE corr, on a 3.6. Your's should easily be that w cams and a 3.8. I would find someone in your area w a Good audio knock detection device to monitor while you are tuning this if you are going to get aggressive on ignition timing, I read you can piggy back the stock sensors so your 993 ECU can still share the info.

Good luck
Kevin
GAS Motorsport
I'd say from shape of your Power curve the Tqe being so high at low RPM 2500-4K, this is where V ram shines and make a great streeter package(though really heavy) and your system i swokring properly in that range. Check the rest at higher RPMS WOT. .

[JoeMag]

...regarding the 944 turbo injectors, they have the capacity.

I ran them on similar motor (same P/C's as you have), 964 heads w 993 RS Valves, 993 RSR cam, 964 plastic intake (weak link to making more power) w fuel press regulator, straight pipes. Motor made ~315hp (@6.5k) and ~270 fts-lbs (@5.5k), dynojet SAE5 corr'n. ...I was mixing premium and 100 (do not recall ratio, maybe 50/50?) with Motec so I could tune. AFR's 13 and below.

[Black 993]

What's the general HP threshold on a 993 engine for needing to upgrade injectors? Have not heard much discussion of this. (I have a 3.8 w/ heads and cams)

[JoeMag]

Regarding what 993 injectors can support, do some googling as there's many on line calculators to calc how much HP injectors can support. ...I pulled up one and based on numbers Bill gave, they can support ~220 @80% duty cycle, ~270hp at 100%. ...target is typically 80 max.

[-Levi-]

Hey everyone.
I just got the chip back from Steve Wong, he made adjustments based on the info from the first dyno. There are two dyno runs here, the blue line is with the exhaust flap open (loud) and the red line is with it closed (quiet.)
We gained between 4-9 ft lbs torque over the last run, hp was the same.

As far as AFR go, we are mid to low 13s to high 12’s depending on the exhaust setting and rpm.
Would these numbers be sufficient to drive the car as is on the street and Drivers Events? Thoughts?

[winders]

The blue line seems too lean to me…I wouldn’t run that AFR on any of my engines.