Hey guys I know this topic has been discussed extensively on this forum, but the search function isnt' working, so I was hoping you guys could help me out. My brother is in the middle of purchasing a white 02 turbo (pictures to come within the week!). But he test drove it tonight and it was only pushing .6 bars in North Carolina(60 degree weather). I thought a stock pushes .7-.8 bars??? Any help would be appreciated!

 

Peak boost or just normal boost? A boost spike is just that: a spike.

Here is the stock boost curve for the K-16 turbos at 1 atmosphere:



As you can see, it peaks at 0.8 for a split second, drops to 0.7 bar for a little longer then sits at 0.6 bar for the majority of the rev range. It finishes off at 0.7 bar by redline.

Now, your peak boost will be affected by temperature, humidity, etc. Try to do your runs in 5th or 6th gear @ 2500rpm. Punch it from that rpm in the higher gears and you should see your peak boost. If you still only hit 0.6 bar, then you probably have a leak somewhere. My first guess would be the diverter valves (the stock ones suck).

 

Thanks for the quick response. I'm going to relay this info to him. Take care

 

Have a similar graph for a stock X50 car?

 

I'm sorry, but I don't. I would be curious to see that graph, honestly.

 

I would be too...this morning the turbo peaked at 1.1 bar! Hitting 1.0 bar is pretty consistent today, only when theirs one person in the car(compared to when the 300lb sales person was riding shot gun before(@.6 bars).

 

My first gear pulls a 1.1 consistent, 1.0 bar or maybe a 1.1 spike in 5th or 6th with a load ont he turbo's and .9 steadily through 2nd, 3rd or 4th.. Is that normal for stage 2?!?

 

Yep. You will have a hard time getting peak boost in 1st and 2nd gear especially. Your RPMS will run out before the turbo has time to spool and control itself. I would think that you should get higher than 0.9 in 3rd and 4th, though. It depends on what your peak boost is set for via the chip. It will also depend on your mods, gas quality, air/weather conditions, etc.

 

Yea i would love a constant 1.0 bar in every gear with spikes, but i guess it wont happen. I am going to reflash my ecu to an updated version, hopefully it might be a little better, im on 93 octane and weather is "warm" for an NY winter but still cold to cali, fla and so on haha

 

Hey Ruiner - gonna have to teach me a little about how to read that graph. I can't relate to the vertical scales as you do.
thanks
bob

 

That's a FAT torque curve compared to an X50 car. A stock X50/S/GT2 gets peak boost at 3,000 RPM.

 

1. Boost curve
2. Horse power
3. Torque

The stock boost curve is at 1 atmosphere (not bar) I do believe, so you have to subtract that out from the total number that you see. There is a conversion factor, but you get the "gist" of what it is saying via my explanation.

 

Smaller turbos spool faster. Assuming that they can hold said boost to redline, you will get a less "peaky" boost curve (if you would like to see peaky boost curves, look at the large single turbo MKIV Supras for an example of that).

 

UPDATE, even witht he warmer 45 degree plus weather today, i noticed from 1st to 2nd i was pulling 1.2 bars, then towards end of 2nd gear i was boosting a 1.0 bar flat, third the same then tapered down to .9 then 4th 1 again, highest boost ive seen in the car thus far

 

A true test of your "constant" bar reading will involve pulls in 5th and 6th gear. 1st isn't a good test as the rpms run out before the turbos really have time to spool and settle down. The same can be true with 2nd as well.

Put your car in 5th at about 2500rpm. Then, go WOT and watch the boost climb and then settle off. You can try this in 4th if you do not feel comfortable (or have the road room) to do this in 5th or 6th. The higher gears put a higher load on your engine and give you a more prolonged, accurate reading on boost.