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Old 02-15-2010, 07:20 PM   #1
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Default Question about my build-What would you do?

So I am slowly moving toward putting together my build.
MSM currently with GT2871 on FM manifold and DP
I have the head finished-mildly ported with custom 274 integral cams. 1mm oversize valves with supertech valve springs and retainers(shim under bucket)
The bottom end is 8.6 Supertech pistons with h beam rods from 949racing and ACL race bearings and all friction surfaces WPC treated.
The intake manifold is a custom piece from Flipside customs with a 70mm mustang throttle body, FM intercooler.
The exhaust manifold with an Absurdflow tubular manifold with Vbands. I have decided to stay with the GT2871 rather than bump to a 3071 for now
750cc injectors with a FM fuel rail, walbro and 750cc injectors
Cooling is a Koyo 55mm radiator, M-tuned coolant reroute, oil cooler
The EM is a Hydra 2.5

So, to my questions. I have already spent quite a bit more on this car than intended and I have decided for now not to go for massive levels of power maybe 320+ if I get there. But, I would like it to be reliable and since I am a perfectionist and have read varying levels of fear about how det prone these motors are I was wondering which direction I should go.
Option 1-I am having EGT bungs installed for each cylinder for tuning as I believe the Hydra has separate fuel trims for each injector. I should be able to get a couple more EGT probes(I have two) at least for tuning. Somewhat expensive but probably not as much as #2
Option 2-Just install a Hydramist system for additional protection but this adds another layer of complexity/point of failure. I wouldn't be using this as a power device, rather just for det prevention.
Option 3-I will definitely make some det cans but was wondering if people had experience with aftermarket Knock detection amplifiers like Gizzmo/Phormula(?)/HKS. I have a TXS knocklite on my subie but that system is pretty limited.
I suppose I could do all three but my wife might attempt to kill me again and what good is a fast car to me if I am dead?
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Old 02-15-2010, 11:36 PM   #2
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Originally Posted by kaisersoze View Post

So, to my questions. I have already spent quite a bit more on this car than intended and I have decided for now not to go for massive levels of power maybe 320+ if I get there. But, I would like it to be reliable and since I am a perfectionist and have read varying levels of fear about how det prone these motors are I was wondering which direction I should go.
Option 1-I am having EGT bungs installed for each cylinder for tuning as I believe the Hydra has separate fuel trims for each injector. I should be able to get a couple more EGT probes(I have two) at least for tuning. Somewhat expensive but probably not as much as #2
Option 2-Just install a Hydramist system for additional protection but this adds another layer of complexity/point of failure. I wouldn't be using this as a power device, rather just for det prevention.
Option 3-I will definitely make some det cans but was wondering if people had experience with aftermarket Knock detection amplifiers like Gizzmo/Phormula(?)/HKS. I have a TXS knocklite on my subie but that system is pretty limited.
I suppose I could do all three but my wife might attempt to kill me again and what good is a fast car to me if I am dead?
I wonder if you might be better off with individual cylinder O2 and a single EGT in the Turbine Inlet position (TIT). I run 6 cylinder EGT w/twin TIT on a Lycoming aircraft engine in order to be able to run lean of peak EGT (LOP) at cruise; I'm not sure that I would want to rely on EGT for trimming fuel dynamically in a changing load environment (aircraft engines at cruise run a single fixed high power setting for hours at a time).

If you run individual cylinder 02s, you can use the TIT temperature as a safety valve; most exhaust turbine wheels have a do not exceed temperature of 1,650 to 1,750 degrees F. Alternatively, you could run 4 cylinder EGT and do some datalogging at high load on a chassis dyno to determine the EGT spread between cylinders. Once you know the EGT spread, you can have the individual injectors "flow tweaked" to minimize the
EGT spread between cylinders (this is how aircraft engines are tuned to safely run LOP).

Jeff C is currently finishing up a batch of electronic det cans, you might want to contact him about getting one. The high quality commercial versions are fairly expensive; some run well over $500 if you opt for noise cancelling headphones.

If you run any water injection system, it is a good idea to have some positive warning system if the system runs out of fluid or doesn't inject the fluid properly.

At the end of the day, the best way to protect your engine is to have it tuned conservatively (e.g, with timing below MBT) on pump gas by a professional using a known good knock detection system. If you go to drag race or open track the car, you can either add race gas or pull 2-3 degrees of global timing to preserve safety margins.

Last edited by sn95; 02-17-2010 at 12:12 AM. Reason: added info, corrected TIT specs
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