this might be a stupid question, but would headers improve the spool time on a GT42 ST setup? if so, has anyone done it and what improvements, RPM wise have been concluded? Thank you.

Alfredo

 

IF there is enough room, and your piping is correct, Sound Performance does make a quick spool valve for this purpose....

Just don't know how much room you have.

http://www.spracingonline.com/store/...ool_Valve/3659

Tom

 

what kind of Boost controller are you running? The apexi avcr and blitz boost controllers have been shown to improve spool up time and boost response.

 

50 shot of n20

 

 

Depending on what boost controller you have, you can have your wastgate stay closed while its spooling up then start opening as it starts to get close to your target pressure. It makes a big difference in my rear mount turbo setup.

 

why would your wastegate even be open below spring pressure? if you have a 1bar spring etc, a boost controller isnt goin to affect spool

 

Just because you have a 10psi spring in there dosnt mean its closed till it see's 10psi. They slowly start opening before that 10psi, by removing the WG's boost reference while it spools up it will stay closed completely. Increasing torque, and faster spool up.

 

in regards to headers........a generic set of headers will probably not do much for you.

If you have a set of custom turbo headers made for your engine's needs, then yes. If properly designed, the pulses in each tube will not be crashing into eachother, but will actually be working together to better utilaize the the exhaust pulses to spin your turbine wheel. Ultimately, you need to find the balance point between max high rpm capabilites and quick spool time. a properly designed turbo header will be setup to maximize your goal. If spool up time is most important to you, you will sacrifice all out max power at higher rpms. and the opposite is true if max top end power is the main goal.

 

I just looked at the Apexi website and I see they make that claim. I could find no data on their site to back it up, however. Here is their claim:

"The valve movement (Boost Duty Cycle) can also be modified. Raising the duty cycle increases boost response, while lowering the duty cycle will slow boost response. This feature allows boost response adjustment for varying turbo sizes. Since larger turbos take longer to spool up ( bad low end response) the duty cycle should be raised under lower RPM's for better response."

Essentially, their claim ignores the fact that all boost controllers (at least the ones I am aware of) keep the W/G closed until the desired boost level is reached. Hence, they don't even effect the turbo spoolup. During spoolup, the boost controller is generally irrelevant (assuming the boost controller is functioning properly). It only becomes relavent when the desired boost level is reached and they start to open the W/G, at which point the turbo is already spooled. So, no offence to you GBoger, but I am calling Apexi's claims as they I see them.



I haven't looked at the blitz controller, but I'll bet it's more of the same. EDIT: See Below - the Blitz controller does indeed perfrom well. I would take the Greddy Profec B over the A'pexi, though.

 

Now, here is a claim that is backed up with actual data. Nice job SP!!!!!!

This is the direction I would go...

 

Thats my understanding as well. spool can be altered from timing changes, but it is what it is more or less until you get close to spring pressure. With a gt42, you'd imagine its a pretty heavy spring (>1bar)

 

Cutting the boost reference to the WG completely WILL improve spool up, then once your getting close to you target boost you allow the boost reference to go into the WG. Otherwise if you are just going by spring pressure, the WG will start opening way before the set spring pressure, it dosnt suddenly open when it reaches the spring pressure. Some controllers are just bleed type and dont cut the reference as the turbo spools up, which is why adding the correct controller which does, improves alot.

 

^^^^

I'd like to see some data showing the comparison. Do you have a link to actual data?

The amount of energy extracted from the exhaust gases for the boost reference should be minimal. Perhaps I am wrong about this, but I don't think so.

I just searched their site again, and I can find no data backing up their claims. I also did a brief search of Google, but did not see anything. It seems to me that if their controller really did what they say it does, they would provide data to back it up, like SP has.

EDIT: I found a site that reviewed the A'pexi AVC-R along with other boost controllers: http://www.modified.com/tech/0207_sc...ion/index.html



Here are the A'pexi graphs:

Here are the Greddy Profec A graphs:

Here are the Greddy Profec B graphs:

Here are the HKS EVC EZ graphs:

Here are the Blitz SPC-iD graphs:

I'm not seeing a significant difference in spool up time between the various controllers, but the A'pexi, Blitz and Greddy Profec B do not overshoot the target boost level like the Greddy Profec A or HKS EVC EZ going from 4500 rpm. The Blitz, however, does get the the target boost level a bit quicker and quickly levels out. So perhaps they can claim that they provide quicker spoolup. The A'pexi does not seem to stand out as being very special, though. Maybe it gets just a hair quicker spoolup, but nothing significant, or anywhere near what SP's spool valve provides. The Greddy Profec B seems to be the most accurate, at least based on this test.

EDIT EDIT: Evidently they had problems with the HKS EVC 4, and did not post the graphs. I previously mistakenly identified the EVC EZ graph as the EVC 4 graph, but this was incorrect. Hopefully the EVC 4 works more like the Greddy Profec B, because that is what I have. I think it does - I have never seen an over shoot on the boost pressure.

 

What makes it work is that springs are not an on/off device. They are Linear in travel vs force.

see here:
http://en.wikipedia.org/wiki/Hooke%27s_law

the spring in the wastegate is designed to limit the maximum boost pressure and error on the safe side of limiting overboost. As the pressure increase inside the chamber the spring starts to compress and open the wastegate valve allowing the exhaust gas to bypass the turbine housing. The valve should be designed to be fully open at the desired PSI. If you cut the reference to o psi until the BC sees 10psi then you have eliminated this exhaust "leakage" and spooled the turbo quicker then if the spring started opening slightly at 8psi and full open at 10psi. The hard part is that you also have to fight overboosting.

Most BC's are PID based and will try to hit the target without overshoot and have a quick settling time. You can tune your BS for better results.

 

^^^^

I'm not sure how much boost leakage is an issue. Based on the data shown in the graphs above, the A'pexi does not appear to allow the turbo to spool up noticably faster than the other boost controllers (maybe it has them by a very small percentage, but not much). Again, I think the energy extracted from the exhaust with the "leakage" is minimal. Otherwise, the A'pexi should be performing quite a bit better that the other controllers, but it does not. In fact, the Greddy Profec B appears to perform better overall, as does the Blitz.

 

We need a comparison of WG spring pressure with out BC and WG Spring Pressure w/BC for the apexi and not comparing it to other BC's

 

I'm not sure of the point in that. The question I was addressing is whether A'Pexi's particular boost controller allows the turbo to spool up noticably faster than other boost controllers. Perhaps I should have been more clear on that. Nonetheless, it doesn't. The data speaks for itself.

EDIT: I think I misunderstood what you were getting at. I thought by leakage you were talking about the exhaust pressure going to the back of the W/G valve. If I am now understanding you correctly, you are talking about the leakage through the W/G when the spring starts to open when there is no pressure on the back of the valve (no BC). That will be an issue without without a BC. That, however, is not what streetzlegend seemed to be getting at. What he stated is that removing the boost reference to the WG completely until it is needed, which apparently A'pexi does, will improve spool-up. Initially, that sounds like a good theory until you think about how much energy is actually being used to help keep the W/G closed in comparison to the total amount of energy contained in the exhaust gases. If it were significant, then the A'pexi should spool quite a bit faster than the other boost controllers. The data shows that it does not (at 5 sec. it may be 0.2 psi higher or so), which supports my contention that the amount of energy is minimal.

 

I dont have saved data, but I have been tuning my car for years and have ALWAYS noticed a difference between no reference while spooling up vs. with reference line hookd up. Just recently I put in a larger turbo which takes more work for it to spool up, i closed the WG completely and noticed it come in quicker. When I have time ill do back to back comparison with WG getting reference and without (ill put up screenshots of my graph from the Emanage). Also, you dont get an insane amount of spool up from this, but it is def something you do notice.

 

without quoting a bunch of people, streetzlegend is right.
like cux350z, said, springs are linear. for example, i have 5.5psi springs and a greddy profec b spec II. There is a setting called "set boost" or "start boost" (don't remember which) which is the pressure that you want the wastegate to start opening at. The exhaust pressure is not released "immediately", so if you set this number too close to your max pressure, you will have a boost spike occur while the exhaust pressure is released and the turbo continues to spool. Regarless of weather the set boost is adjusted or not, the max boost you have set will be the same. the wastegate will just open much faster closer to the max pressure instead of slowly opening as pressure increases.
Most ebc's i've seen do have this feature, including the greddy profec b spec II and the apexi avcR.
but this cannot affect when the turbo starts building pressure, just how early you reach max pressure.
maybe i'll play around with it this way to prove the point.. my w/g springs are 5.5psi. in theory, using the boost controller to set the same psi as the spring is should spool the turbo faster. This will be a harder test on such a weak spring, as i can't set the start boost much closer to 5 psi, but i should be able to a) see max boost at a lower rpm and b) hear the wastegates open later, instead of that wimpy exhaust leak sound as they first start to open with my open dumps

i hope everything i said was accurate, i typed fairly fast

ross