Matt
yeah, what makes you think my exhaust is restrictive? [img]images/smilies/mad.gif[/img]

Pete
I did read it all - but it still wasn't 100% clear. It is now - I remember

BTW, nothing wrong with my boost at high revs - there's shedloads of it everywhere - don't believe everything the geek's software tells you LOL

 

Richard

No, the twin dump downpipe isn't desned to restrict the gas flow out of the wastegate to keep boost levels up at higher rpm. What's actually happening is that the lack of backpressure at higher rpm is allowing us to get the boost levels we wanted anyway. During our testing we found that the final design (as we are fitting to the STi) with the right catalyst and as importantly the inlet and outlet cones gives more boost at higher rpm than a completely catless design with identical twin dump design off the turbo.


Pete

That's our ECU managing the boost levels to achieve what we want to see. Even at low rpm this is the case and boost figures from Delta Dash or select monitor may not be what is actually happening in the manifold.


Mike

 

Chaps,

When I said restrictive, I was talking in relative terms. Working on the assumption that all exhausts are restrictive to one degree or another, the standard STi exhaust is very restrictive, the PPP and Milltek less so, and any decat exhaust less than that. Is this incorrect? I would imagine the laws of physics would state that any object placed in the air flow (such as a cat) would create a "restriction". Does that explain what I am talking about?

Ray,I would disagree. A decat exhaust with a restrictor will have a slower spool up than a.n.other exhaust with restrictor and/or ECU remap as using just a restrictor is usually a trade off. You can have fast spool up with possible boost spiking or you can have slower spool up with less or no spiking. The Boost maps and restrictor are designed to work with a particular exhuast system with a certain amount of restriction. If you change this then the ECU can only cope to a degree by itself, with it's current maps..Your theory is correct but in practise, I don't think you can get the same spool up as the PPP/Milltek (and maintain proper Boost control) with a decat system (on the STi with no other mods anyway), without modifying the Boost maps.

Remember Boost is only one of the parameters that creates power and torque. Ignition Advance and fueling are the other two. Boost is not the be all and end all.

Matt

 

OK fair enough,

So what you are saying is that ScoobySport should can their decat system, stick a cat in it so they don't need a restrictor then they will get faster spool up like PPP and Miltek and thus a better zorst system ?

Cheers,
Ray

 

LOL at Dave's distrust of geekware

Ta Mike. It looked too jagged to be a true reading.

It will be interesting to see what Ecutek achieves with this ECU. I have seen the WRX maps/outputs and they look very good.

 

Matt

We are getting into the black art of exhaust design here, but bear in mind that the surface area of our cat is four times as much as the std pipe and three times as much as a 3" pipe. From that it's fairly safe to say that the cat is not going to restrict gas flow at the cell density we are using, particularly as the inlet cone design we use makes sure that full flow is achieved across the whole surface of the cat.

We also found that this downpipe design is remarkably quiet as well, probably due to the huge cat volume and relatively slow gas speed through it (larger diameter=slower gas speed for same volume of gas)

Regards

Mike

 

Pete

Ray
I think you will end up disappointed if you try to chase 300ft/lb of torque with restrictors only

All
I understand there is a RR day at Powerstation for STi7's on the 16th Nov. Whilst i'm not a fan of RR sessions (I could be out driving the car instead ), and won't be there, it will be interesting to see the torque figures achieved if there is a good mix of mods there

 

So Dave T-S what would be your fair guess for torque on a JDM STi-7 full SS turbo back decat ? 265 - 275 lbs ?

Come one man, surely it sees 290 lbs ?

Cheers,
Ray

 

Ray,

That's over simplification. You could argue that it is extremely difficlt to design a decat exhaust for the STi which needs no restrictor change, and doesn't cause any Boost spiking. In Pete's case, his fix is to use a restrictor to control spiking but at the expense of spool up. This is one solution and for the money, you can't expect anything more elegant than that, after all, the PPP goes the next step and costs around £1000 more, for good reason.

Dave, geekware is only as good as the geek master's information, in this case the ECU : ())

Mike, "The Black Art of Exhaust design" - LOL Indeed - that's what makes it such a challenge to understand When you say:are you saying that it really is oscillating (sp?) like that at the top end (didn't see it on Dave's gauge and as you know, you can't feel it on the road)?How is this the case? Does the PPP drastically modify the manifold pressure signal as opposed to just capping the peak figure (which is what I thought it was doing)?

All very interesting and thanks for getting involved Mike

Ta,

Matt

 

Matt

The signal is not capped but it is modified. The real boost figures if you saw the raw data going into the ECU are smooth.

Mike

 

Ray
No idea! Have you got access to a rolling road? If no, I can say what I like and you can't dispute it LOL

What is standard JDM torque on a totally standard car?

What octane gas are you using?

 

Matt

I may be wrong (reaches for Nomex) but don't the WRX and STi PPP boards just up the boost and let the standard maps sort everything else out?

Matt, shame you haven't got a log of a full Scoobysport system. Its quite a bit different to Jonnos and will show a similar spike around 3000/3200rpm. Jonno runs a 1.3mm restrictor to contain the spikes on his (APS filter and HKS rear sections). On our standard set up, this is much too big.

 

Mike, not trying to argue, but are you also saying that solenoid DC isn't zero, it's only the ECU thinking it is ?

 

EvilBevel

No, that is not changed

Mike

 

Thanks Mike.

I realize you don't want to give away the whole game, but is it fair to say that since DC is pretty much zero at higher RPM, it is the wastegate / max flow through the wastegate & exhaust that is determining the actual boost pressure (regardless of how DeltaDash/select monitor reads the MAP signal) ?

Not trying to get into a ware of x vs y, just trying to understand the techy side.

Theo

 

Theo

On that log, probably yes is the answer to your question.

Mike

 

Pete,

Just spoke to Jonno conincidentally about something else and you're right, I completely forgot that he has a SS up-pipe and 3inch SS DP, an HKS centre and back (3inch) and an APS induction. I got the restrictor size wrong too, it's as you say, 1.3mm not 1.25. Now it's getting colder, Jonno is seeing regular 1.35-1.4 peaks whereas before the restrictor change, was seeing sometimes 1.5-1.7 (held) (he got some cracking power figures @ PE whilst running this boost though )

I did put out a call to see if there was anybody out there on a standard JDM STi a while back and also an STi with a full SS system, so we could compare them also but nobody answered. After all, what's in it for them? Havind said that Pete, Deep Singh and I were going to get together but my holiday got in the way, what combo does he have again?

Ta,

Matt

 

Thanks Matt, I think Ray was looking at the graphs and thinking he was mising out. I wouldn't expect Jonnos car to be spiking at all in 4th with a 1.30mm. His set up is geared much more towards overall power, which is what was after.

What power did he get then?

Deep's car will be a good one to do. It drives really well with boost contained at 1.25bar.

 

Thanks Mike.

 

Matt

Deep has a full system with up pipe and is running a 1.25mm restrictor.

 

Ray

I think you will have to look at ECU work to achieve this

 

Ray

Hang on for Ecutek 01/02. Its available at the end of Nov.

 

I have just read the other thread that Matt has put up, about DD logging on STis.

Never one to be controversial I've done my own bit of "manual correction", does anyone want to comment on this http://www.scoobynet.co.uk/bbs/threa...=147454&Page=2

 

why dont you use a bleed valve configured to act as a tap blocking the leak from the actuator, so that you can restrict maximum boost?


it seems that any minor changes are affecting your boost control (as you would expect), but that way you would not need to mess around withy restrictors all the time, you could simply tighten the bleed valve as the overboost sets in with the cold weather surely?

 

Ecutek sounds good unfortunately I don't think I can leave my car undrivable for however long it takes to get an ecu from Nassau to UK and then wait for for the new one to arrive back in Nassau ?

Suggestions ?

Cheers,
Ray

 

Ray,

That's a tough one TBH! I guess your best course of action is to install a flow valve like Adam suggests and you can taylor your "restrictor" to whatever suits you. But like we have said, you'll always have the compromise of spool up vs spiking.

The only other option would be to fit something like an Apexi AVC-R which is an aftermarket Electronic Boost Controller which allows you to map Boost Solenoid Duty Cycle by rpm zones. In this way you could have a faster spool up (like having a smaller restrictor) with less spiking (like having a larger restrictor). I'm not sure how likely this will solve your problem as I'm not convinced Boost controllers on the new ECUs are the right way forward but it may be worth a thought. Havind said that, I heard that they can be quite tricky to setup and don't know if a) you're up to it and b) if there is anyone on your island that could do it for you (even if it is a good idea).

Anyone else have any thoughts on the matter?

Matt

 

Cheers for the idea....anyone else ?

Ray

 

Ray, mail John Banks about the ECU - he may be able to help.

Bearing in mind I am struggling to understand this thread, the following may or may not be relevant...

I have been playing with restrictors to control boost levels and spikes and they work fine. But now, on JB's suggestion I have a Dawes MBC doing the same job, which it does very well, but it is obviously adjustable according to conditions and has other benefits, too.

Don't ask me to explain how... John?

Cheers,

Richard.

 

Somehow I feel a Bahamas mapping trip coming on for JB, dunno why

 

LOL, EB