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Old 06-23-2006, 12:37 PM   #1
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Default How much boost

I should have my setup running today/tomorrow (no pictures unless roman stops by with his camera) And my question is, how much boost can i run without an AFPR and fuel pump? Im not looking for max, but a safe 2psi would be nice (to check for any major fab mistakes.
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Old 06-23-2006, 01:24 PM   #2
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Yeah, maybe 1-3 psi, maybe. I'd toss in some toluene and/or crank your timing way down.
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Old 06-23-2006, 02:10 PM   #3
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how much timing to pull? Whats everyone ideas?
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Old 06-23-2006, 02:40 PM   #4
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Old 06-23-2006, 02:43 PM   #5
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My 2 cents...let's just assume that you plan on running at 2 psi:

I don't think that your problem will be heat/timing. Running 8 degrees of base timing and 91/93 octane will probably be sufficent. If you really wanted to be cautious, you could go to 6 of base timing.

Big problem (obviously ) will be fueling. I looked at my base dyno for a 1.6, but the 1.8 is similar in terms of stock ecu fueling. Car runs in closed loop up to about 4k rpm and it shows as an afr that hovers around 14.7 before 4k rpm. I'd avoid boosting within this range b/c your stock ecu will shoot for an afr of 14.7 here which is on the lean side for FI, but who knows, maybe this is a good place to test as the ecu would add fuel to try to get to 14.7. I'm not sure. I'd also be careful around 5300 rpm b/c that is where the HP/torque curves cross and the car will be more prone to detonate. So...if you were going to test it out, your safest bet is above 5500 rpm where the car is in open loop and runs on the richer side already. My stock afr above 5500 rpm was 12-12.5 and lower at higher rpms. That does not guarantee you safety and I know it doesn't give you much of the rev range to work with, but based on the A/F ratio of a stock computer, it's the safest place to "try" it.

Also might be worth it to check out your base pressure of your stock fuel pump. You figure most people find that a base pressure of ~44-48 + 6 psi of fuel per psi boost (as a rule of thumb) and you would need around 56-60 psi of fuel at 2 psi of boost. If your base pressure is on the low end, you might want to reconsider.

Finally, the ghetto method would be to disconnect your o2 sensor. Your car with idle like crap and throw an error code, but the car would run in safe mode and dump in fuel like crazy.

I'd probably wait, but I know that's pretty damn hard to do...
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Old 06-23-2006, 04:16 PM   #6
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then ill probably just tie the wastegate open. Thanks for the response.
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Old 06-23-2006, 04:45 PM   #7
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I tied my internal wastegate open and still made boost. ymmv - So watch you're gauge.
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Old 06-23-2006, 07:49 PM   #8
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2psi, is actually going to be like 12, since you probably pull 10 psi of vacuum when running NA. Good luck burning stuff up.
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Old 06-23-2006, 09:12 PM   #9
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Seems a better idea not to try it at all without at least an AFPR. My testing on the stock FPR showed that boost pressure over atmosphere had no impact on raising fuel pressure.

Removing the O2 sensor would have no impact since it only adjusts fuel in closed loop.

If wishing to check for leaks in the plumbing, suggest a simple vacuum test. The -21/22"hg is easier to see abnormalities in than 2 PSI of boost.

If you really really want to do it suggest partially pinching the fuel return hose closed so the fuel rail reads about 55-60 PSI at atmosphere manifold pressures. One bandade deserves several more.
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Old 06-23-2006, 09:32 PM   #10
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Quote:
Originally Posted by Pop VII
Removing the O2 sensor would have no impact since it only adjusts fuel in closed loop.
Actually, when the ecu does not get an o2 sensor signal or the sensor grounds out, the ecu defaults to a safe mode that throws in a ton of fuel so you can "limp" home without damaging anything. Ask me how I know.... I think I used half a tank to go about 30 miles....
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Old 06-23-2006, 10:11 PM   #11
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Quote:
Originally Posted by hustler
2psi, is actually going to be like 12, since you probably pull 10 psi of vacuum when running NA. Good luck burning stuff up.
what are you talking about? no offense

if you noticed, the boost gauge isnt measure in psi below "0"
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Old 06-24-2006, 03:06 AM   #12
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Quote:
Originally Posted by brgracer
Actually, when the ecu does not get an o2 sensor signal or the sensor grounds out, the ecu defaults to a safe mode that throws in a ton of fuel so you can "limp" home without damaging anything. ...
Yes, a safety map will ignore the O2 signal and make things run richer anyway ... but not really really rich. The O2 sensor in the 1.6 plays a very small role compared with many other vehicles ... but then is leaning out the mixture and only in closed loop operation. The majority of driving is done in closed loop, and the only time the signal is used and not ignored by the ECU. So the O2 sensor plays no role until the engine is warmed up to operating temperature, at idle below 1.5K RPM, or when conditions of WOT and 4 K RPM are met. In most practical instances will not be in boost during closed loop.

By pinching the return fuel line a bit will raise the fuel pressure some across the board attempting to make all modes run richer ... the advantage is the O2 will lean out the mixture during closed loop.
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Old 06-25-2006, 02:10 AM   #13
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Can he retard the timing to say 6 degrees and run higher octane gas to keep it at 2psi or so? We have 93 octane everywhere around here and the station by my house has 100 octane unleaded.
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Old 06-26-2006, 12:55 AM   #14
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I would say no as the higher octane and the timing change serve different purposes. Neither will provide additional needed fuel.
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