Stage 3-, possible alternative to MBC (longish)
03-18-2004, 06:39 PM
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Stage 3-, possible alternative to MBC (longish)
I wonder if anyone has thought of this idea for running stage 3- without an MBC.
The reason for the MBC is that the bigger turbos spool late and very rapidly and the ECU feedback loop is not fast enough to keep the boost in check. The result is that it spikes quite high then recovers.
I see that VW guys get "Race N75" valves that give you more boost by opening up the bleed port on the boost solenoid. This causes the same effect where the ECU cannot keep the boost in check and it overshoots. (Terrible idea, IMHO)
So, what about using the stock electronic boost control, but restricting the bleed line of the N75, perhaps with a needle valve? That means that the stock feedback loop should effectively be faster because there is less bleed off so the actuator will move sooner.
This system would allow you to retain the stock boost control (very elegant IMO) without the boost spiking problems. Now, if the requested boost is reduced at higher RPM's (in anticipation of K03's being flowed out) you would still have that reduced boost vs. an MBC. But, you are probably risking outflowing the injectors or hitting fuel cut at that point anyway.
Just a thought. Wanted to know what people think. I think I am going to be in the position of needing a stage 3- solution myself in the relatively near future.
Thanks,
Karl
The reason for the MBC is that the bigger turbos spool late and very rapidly and the ECU feedback loop is not fast enough to keep the boost in check. The result is that it spikes quite high then recovers.
I see that VW guys get "Race N75" valves that give you more boost by opening up the bleed port on the boost solenoid. This causes the same effect where the ECU cannot keep the boost in check and it overshoots. (Terrible idea, IMHO)
So, what about using the stock electronic boost control, but restricting the bleed line of the N75, perhaps with a needle valve? That means that the stock feedback loop should effectively be faster because there is less bleed off so the actuator will move sooner.
This system would allow you to retain the stock boost control (very elegant IMO) without the boost spiking problems. Now, if the requested boost is reduced at higher RPM's (in anticipation of K03's being flowed out) you would still have that reduced boost vs. an MBC. But, you are probably risking outflowing the injectors or hitting fuel cut at that point anyway.
Just a thought. Wanted to know what people think. I think I am going to be in the position of needing a stage 3- solution myself in the relatively near future.
Thanks,
Karl
03-18-2004, 06:43 PM
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Would be worth a try, but ultimately an MBC in parallel with the N75 would suffice too.
But with the tapering to redline, you won't be maximizing the upper RPM flow of the K04's.
03-18-2004, 06:46 PM
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I like people like you...
Couple of things:
1. I would be worried about wastegate flutter, since it would take alot less pressure to open the waste gates.
2. If your run the MBC in parallel, like i did on my old car, it cuts off the spike, and then lets the N75 take over. This actualy worked out really well. I pulled 2-4 cars on stage 2+ cars.
1. I would be worried about wastegate flutter, since it would take alot less pressure to open the waste gates.
2. If your run the MBC in parallel, like i did on my old car, it cuts off the spike, and then lets the N75 take over. This actualy worked out really well. I pulled 2-4 cars on stage 2+ cars.
