Yes I know that no one runs them with their high flow aftermarket fuel systems and do just fine. However, I am still intrigued by this aftermarket option offered by Radium Performance. I have personally seen this phenomenon in our engine dyno lab on high pressure common rail diesel fuel systems and we use an OEM grade rail mounted fuel pressure damper to smooth it. It has helped tremendously. The fluctuations observed in a common rail diesel are more significant and primarily a result of the cam mounted high pressure pump. You index it according to injector firing times to reduce this but also use the pressure damper.

I would like to see some high speed fuel pressure data from a gasoline engine with and without one though. Does anybody have this? Also does anyone run one of these?

http://www.radiumauto.com/Fuel-Pulse...Kits-P751.aspx

 

Bear in mind the ridiculous pressure difference between common rail diesel and normal gasoline injection. I don't believe there is any way to make an apples to apples comparison.

 

There was a guy on the truck forum that developed a miss at a certain rpm regardless of what he changed. Ended up being caused by pulses in fuel. Added one of these dampers and it corrected problem. Tried to just search it and link but couldn't find the thread.

 

Hi 240, again more BAD tech ! (NOT YOURS or Long Blue)

The GM OEM Fuel Rails have internal Pulse Dampeners that look like a " LONG stick of gum" inside the rail.
My Rails are 11/16" bore that allows this type of internal dampener to be fitted.

I have fitter Porsche style External dampeners REQUIRED after finding the Fuel Rail Pluses SO BAD that fuel AFR went OVER SCALE unable to be measured. (LEAN)

I can provide the required fuel rail dampeners ?

Lance

 

If I am wrong about something I would prefer to just be told that outright. So far I have yet to find one of your posts with any misinformation, so I value your experienced opinion in these matters.

 

Are you actually having a problem that needs fixing ?

I've only ever tested one car where fuel pressure did fluctuate a lot due to removing the damper, but despite the fluctuations, it never had any adverse effect on how the car ran.

It just looked horrible on datalogs.

 

Hi All, I have designed/manufactured DI, GDI, Solenoid Fuel Injectors for many years.
The G-2 was done in 1994 with a supply rail pressure of 5K psi AND an internal 7.1 intensifier. (35K psi)
My first problem was in 1985 with Bank/Bank injector wiring/firing. (Bosch J)
The Fuel Rail Resonance was at 2200 RPM with NO/LITTEL fuel flow out of the injector. (Dampeners fitted/problem solved)
Next "batch fire" Fuel Rail Resonance (8-V again) at 4400 RPM, same problem and same repair method.
Then a CAS was added allowing "True Sequential" injection, the first EMS with a 60-2 TW (58x) and TS, allowed for another increase in Fuel Rail Resonance now to 8800 RPM, same problem, same fix. (SAE Collage Winners in 1989)

The need for a DI "high rail" electronic injector was specified to me by Semens.

What was found : The Rail Pressure 50 psi, 1000 psi, 5000 Psi, 35K psi had little effect on the Fuel Rail Resonance problem as the problem is caused by the opening/closing of the fuel injector with respect to orifice size/frequency.

Lance

 

Pantera EFI - thanks I always appreciate your responses as its clear its coming from another engineering like mind to discuss these things that are often overlooked in the performance world because it usually is "not needed". I know the GM rails have what I like to refer to as the "pea pod" dampers in them. I am actually running larger ID billet rails with 2 separate feeds and 2 separate lines feeding a dual inlet regulator. The larger volume in the rail will inherently behave as a fluid damper, but to what extent? I would really like to see high speed pressure data inside of an undampened versus a dampened rail (whether that be using a diaphragm OEM type damper or an in rail "pea pod" damper) for my own digestion. Batch fire would be a nightmare im sure and our sequential control helps however with large injectors and larger volumes injecting over shorter time frames (pulsewidth), the pressure fluctuations are sure to be more influential. I purchased the Radium vacuum referenced pulse damper for my piece of mind. I still want the data. I will see if I can get my oscilloscope on a high speed pressure transducer with and without the damper in there down the road when I have some time. I will be sure to publish the results for you all to see.

 

Was this on the earlier year 924/928/944 batch fire systems? I recall a damper being imperative on those systems when I had a 944 back in the day.

 

Hi 240, yes again, thanks.
My original knowledge was learned in the first year of the introduction 928, ( I turbo charged this) my first BAD problem case of Fuel Rail Resonance.

I designed my Fuel Rail Extrusion with an 11/16" bore.
I designed my FPR with a large diaphragm to help dampen the pluses.
I designed my rail to allow those "pee pods" to fit inside the rail bore.

I would use/can supply a MPX 5500-DP pressure sensor (7 Bar) for your test.
The response is fast AND your frequency MAX is only 200 HZ ever.
The DSP56f805 is the device that effects my data (16 bit @ 80Mz) report, this is the one I use for my ECU-882C.
I have AUX channels for this input and filters in software for the data read.
I agree that my CRT scope or my Pico Scope (eight channel) would produce better graphs.

The work I do/you do here on LS-1 tech HELPS those who ask us to solve problems. (often unobserved !)

Lance

 

not sure why I'm going to add this, but here it is anyway lol
This is a shot of the damper on Arctic Cat's 800cc two stroke. It makes over 159.0 hp from 7900 to 8300 rpm, with a peak of:
8100 rpm: 160.6 hp, 104.1 ft/lb, 0.634 bsfc, 97.1 lbs/hr fuel, 282 cfm of air, 57.6 psi fuel. (all dyno data corrected to std, not sae)

I bring it up only because they use the same style injection on a 600 cc version of the engine, but without the damper.
8150 rpm: 120.5 hp, 77.7 ft/lb, 0.632 bsfc, 73.2 lbs/hr fuel, 214 cfm (all dyno data corrected to std, not sae)

 

Lance,

Good discussions here, thanks for your response. I have access to hundreds of Omega and MSI solid state pressure transducers in pretty much any signal output and range. Here are the specs of just 1 of the hundreds I have thats currently sitting on my desk:

SPECIFICATIONS
Voltage Output
Excitation: 24 Vdc @ 15 mA (7 to 35 Vdc for 5 V output, 12 to 35 for 10 V output )
Output Gage Models: 0 to 5 Vdc or 0 to 10 Vdc ±1.5%(3-wire)
Output Compound Ranges: 0 to 5 Vdc or 0 to 10 Vdc ±1.5%(3-wire) Vacuum = 0 Vdc, Full Scale = 5 or 10 Vdc
Vacuum Models: 5 Vdc or 10 Vdc at ambient pressure to 0V at full Vacuum
Zero Balance: 0 Vdc ±2% FSO

4 to 20 mA Output
Excitation: 24 Vdc (7 to 35 Vdc) reverse polarity protected
Output: 4 to 20 mA ±1% FSO (2-wire)
Output Compound Ranges: 4 to 20 mA ±1% FSO (2-wire) 4 mA = Vacuum to 20 mA at full scale
Vacuum Models: 20 mA at ambient pressure to 4 mA at full vacuum
Zero Balance: 4 mA ±2% FSO
Max. Loop Resistance: 50 x (supply voltage -10) Ohms



Common Specifications
Accuracy: 0.25% BFSL (including linearity, hysteresis and repeatability)
Operating Temperature: -54 to 121°C (-65 to 250°F)
Compensated Temperature: -20 to 80°C (-4 to 176°F)
Thermal Effects: 0.04% FS/°C (0.02% FS /°F)
Proof Pressure: 150%
Burst Pressure: 300% range <100 psi; 200% range ≥100 psi
Response Time: 2 mS typical
Vibration Sensitivity: At 20 g peak sinusoidal vibration from 10 Hz to 2000 Hz (1.2" D.A.), the output shall not exceed 0.04% FS/g for 15 psi range to 0.005% FS/g for 100 psi and above
Natural Frequency: >35 kHz for 100 psi range
Gage Type: Diffused silicon strain gages
Wetted Parts: 316 SS, borosylicate glass, silicon nitride, epoxy
Pressure Port: 1/4-18 NPT
Electrical Connections:
PX209: 1 m (36") shielded 4-conductor cable
PX219: 9.4 mm mini-DIN 40050 Plug Connector Supplied
Weight: 128 g (4.5 oz)


I also have National Instruments high speed DAQ hardware and LabVIEW if I wanted to record the data, filter, post process, export data, etc. I have a simple single card chassis that would be easy to drive around and record with. I can throw a VI file together quick to record the pressure data, that way I can see whats going on in the rails under all engine speeds and loads, etc. Also see what happens as the secondary fuel pump is kicking on and off under boost.