hey guys, i recently installed a prosport boost gauge and it only shows be holding 10 lbs in the power band. however when im say in 4th at 50 mph and wot itll show me holding 14-15 lbs but as soon as it reaches the power band it drops to 10 and holds. i have cobb sri, inlet pipe, forge bpv blue springs 2 shims. anyone know what could be wrong? car does not feel slow and still beats a stock srt4 by a good measure
possible boost leak?
- Thread starter cjms3
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not necessarily, your on stock tune correct? they each differ a little but alot of people see the dropoff start somewhere between 5k and 5.5k. now if you see it before then there might be an issue with the BPV, but i dont know to much about forge products. but sounds to me like your just another one in the group feeling the effect of the small turbo on the stock tune. if u get an AP or a standback and put a map on it, it will be a different story and you will have power almost all the way to 7k. thats a big step for getting power 2.5k past were you make the power now. might be something you look into once you got some more bolt-ons.
RC08MS3: Could you post a dyno run on your tune if you go that route? I'd like too look at the power curve and the AFR's.
I have to say that I think the flow limitation on the K04 turbo is just that -- a finite flow limitation that a tune cannot fix. I am having trouble seeing how a tune is going to overcome the thermal ineffeciency of that small turbo once you get north of 6k. That turbo just turns into a heat engine when it tries to spool any amount of decent boost from 6k rpm and above.
I'd love to find that I am wrong. But I have a deep suspicion about trusting some of the dyno charts I've seen showing huge gains at 6500 rpm from a tune, considering the design of the stock K04.
If I am correct in my assumptions and calculations based on the known flow characteristics of the KO4 (chart attached), we'd have to be able to flow almost 500 CFM (492) to hold 15.7 pounds of boost at 6500 rpm, when our maximum flow rate turns out to be 371 CFM.
I have the math to post if anyone is interested, courtesy of an engineer on another forum, but will not bore everyone with it at this point. As far as I can tell, there is no mistake in the calculation. To hold boost of 15.7 psi at 6500 rpm on our engine with our compression ratio you just have to have a bigger turbo. No tune would get you there.
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lol wow man, i didnt say you'd have peak power, or tremendous power,i just said youd have power. I think most everyone knows that you wont create that much power with the turbo, but fact is if your on the 1/4mile, if you can stretch your gear a lil longer, instead of having to shift and build boost again, you will run a little quicker of a time.
and even at 14.5psi at 6.5k, you've still got more power than a stock tune that dips to around 10 at the same RPM, a tune will help no matter what, just not make power like a bigger turbo.
and even at 14.5psi at 6.5k, you've still got more power than a stock tune that dips to around 10 at the same RPM, a tune will help no matter what, just not make power like a bigger turbo.
18psiWhiteMS3
Banned
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- 2009 MazdaSpeed3
For me stock boost peak was 15 and held 12 psi by 6k
Once you hit 371 CFM flow through that turbo, you hit the wall. Try to push it to higher rpm you just generate heat through friction. You may be able to hold the boost longer, but you are not increasing flow and you are increasing heat. More heat means fewer oxygen molecules in the intake charge which means decreasing power at the same boost level. That's just my read on the situation.
