TTC & ETTC Mods

Being the curious sort, I tried the TTC Conversion as per the guide on MKIV.com and quite liked it. However I noticed I was getting the dreaded boost spikes, the first one was 17psi!!! , then after that 15psi, so had to back off! (Didn't hit fuel cut though?)

I've decided to have the ETTC mod done, so will I have to get a boost controller fitted?

I haven't got any engine mods so far, so if I do have to get one fitted can anyone recommend one please?

Boost cut contoller (Greddy BCC or similar)

I don't get this: all these 'true twin' mods simply deprive the supra of its main claim to fame: the sequential operation that gives power down low without compromising the top end.

So instead of building on that trait, people cripple it and trade it for absolutely no extra top end

I really don't get this...

Dug i can recommend the one Thor does.

VFCC

I've had mine in TTC for around 6 years now, with the e-manage managing the mapping of the ignition/fueling. The main advantage of the parallel set up, is that you get a smoother power curve and more mid range power. Worth the trade off IMO. I also didn't like the sequential setup, I never quite felt in complete control of the transition to the second turbo, especially when accelarating out of a corner.

Say that, if I didn't have the emanage, then I would stick with the sequetial setup.

Dug, unless you are going to fit some way of remapping the fueling and ignition, I would leave it in sequential set up. The stock ECU is mapped for the sequential turbos, so will not cope well with running TTC. You might want to speak to Ian C, he did a post recently on the subject.

The sense of 'flatness' that you normally get with a sequential BPU car can be fixed with a properly placed/adjusted boost controller on the EBV.

I've done it and it's brilliant. The low-down pickup and feel would kick the ass of any TTC setup, and singles most likely. Neither is there a boost drop during the crossover.

As I said, i'll do the ETTC so I can switch it. I only want TTC for motorway runs etc when fuel economy is an issue. I actually prefer the seq set up, its how the motor was designed, but if I'm going to run in TTC then I want to avoid those nasty boost spikes.

(Liked the LOUDER exhaust tho!)

Actually could be tempted with doing this when i get my new TC. Then onto the strip

Ive got a blitz sequential boost controller. Would this help with the boost spikes with this sort of system?

Surj

I have the switch you need somewhere. Gimmi a shout if you want it and ill look for it!

Holy thread resurrection Batman!

LOL i thought it was 2006 just noticed its 2005! oh well! hehe! Whats the switch for mate?

Surj

The switch will enable you to switch between sequential and true twin mode. I've had this installed now for about a year and tend to run in sequential most of the time, only using TTC on long motorway runs.

How do you over come the boost spikes ive read about?

I believe the boost spikes are a physical result of the TTC mod.

You MAY be able to reduce it by adding a smaller restrictor ring into the exhaust.

The sense of 'flatness' that you normally get with a sequential BPU car can be fixed with a properly placed/adjusted boost controller on the EBV.

 

I've done it and it's brilliant. The low-down pickup and feel would kick the ass of any TTC setup, and singles most likely. Neither is there a boost drop during the crossover.

Any chance someone could elaborate on this? What does the boost controller do? I thought it just allowed you to increase boost.

Any chance someone could elaborate on this? What does the boost controller do? I thought it just allowed you to increase boost.

True, a boost controller cannot reduce the physical boost produced but can increase it.

Boost controllers are expensive bleed valves which reduce the air controlling the wastgate therefore allowing you to increase boost.

True, a boost controller cannot reduce the physical boost produced but can increase it.

(The guy at Weston Performance contested that point with me but I let it go as I didn't understand what he was talking about and he was in control of my car at the time)

Boost controllers are expensive bleed valves which reduce the air controlling the wastgate therefore allowing you to increase boost.

I understand that..but what I mean is why is John saying it makes such a big difference with the standard sequential setup? Is the boost controllable throughout the rev range or something?

How do you over come the boost spikes ive read about?

The spikes occur for two reasons. One, the stock boost control mechanism, and two, the small wastegate.

The stock boost control mechanism works in two ways. Below 4000rpm it uses the exhaust gas bypass valve (EGBV) to perform two functions. One, it prespolls the second turbo by diverting gas away from the first one. Two, this diverting of gas acts as a wastegate for the first turbo. (There is a way of utilising this to increase turbo #1s boost pressure, search for "blue spaghetti mod")

Once the engine gets over 4000rpm the ECU brings turbo #2 online properly, and so uses the wastegate built into #1 to control boost pressure instead. The wastegate is controlled by a VSV which is switched by the ECU, and this VSV stops any pressure reaching the wastegate actuator until 4000rpm is passed.

So, when you go to parallel mode, the turbos spin up at about 3500rpm. The only wastegate control the ECU uses for the next 500rpm is the EGBV, which is futile as all it does is merge with the gas flow already taking place in turbo #2. Therefore you have no wastegate control. Hence, you get a boost spike, which is worse the higher the gear you are in.

The wastegate kicks in at 4000rpm, and here is the second problem - it's too damn small. As we know from restrictor ring experience. So it takes longer than it should to drop the boost back down to a reasonable level, thus compounding the boost spike.

The way to get around this is to plumb in an electronic boost controller and tune it to your setup. Normally they are ineffective below 4000rpm due to the sequential system, but it will be able to control the overall boost in parallel mode as the wastegate will be controlled by the boost controller instead of this VSV the stock ECU uses. So at 3500rpm it will open the wastegate and stop the spike. As the spike never occurs, the size of the wastegate isn't an issue (assuming it isn't in the first place i.e. you have a restrictor ring in place or some other solution) so that problem doesn't show up.

A bleed valve won't have the same effect unless you bypass the wastegate VSV, and you'll be shooting yourself in the foot there anyway as boost buildup will be even slower - as the pressure builds the wastegate will start to creep open and slow the production of boost before your target pressure has been reached. Yes, you'll probably stop boost spikes, but only because it'll struggle to hit full boost below 4000rpm anyway.

I'm no fan of parallel mode, the only person I know who's done it properly is Nic and funnily enough I've not driven his car to see what it's like I must admit though it'd be interesting to map an E-Manage for that, see what could be done.

Hope that helps

-Ian

I must admit though it'd be interesting to map an E-Manage for that, see what could be done.

 

Hope that helps

 

-Ian

you can map mine if you want

So, when you go to parallel mode, the turbos spin up at about 3500rpm.

 

I'm no fan of parallel mode, the only person I know who's done it properly is Nic and funnily enough I've not driven his car to see what it's like I must admit though it'd be interesting to map an E-Manage for that, see what could be done.

What do you mean by spin up at 3500rpm Ian? Do you mean starts to make positive boost then?

Mine make positive boost around 2800-2900rpm.

ps. Oasis are now doing one way budget flights UK to HK from £75, get yourself out here and you're welcome to have a drive. You could also map an EMU for me whilst you're here

http://www.oasishongkong.com/gb/en/home.aspx

Here's an overlay of Terry's (T61), Homer's (BPU stock sequential) and my (BPU parallel) dynos as a comparison.

Certainly not definitive, but it does show some gain in mid range power with the parallel set up.

http://img133.imageshack.us/img133/5206/t61vsbpubm7uy3.jpg

What do you mean by spin up at 3500rpm Ian? Do you mean starts to make positive boost then?

 

Mine make positive boost around 2800-2900rpm.

 

ps. Oasis are now doing one way budget flights UK to HK from £75, get yourself out here and you're welcome to have a drive. You could also map an EMU for me whilst you're here

 

http://www.oasishongkong.com/gb/en/home.aspx

3500rpm is the point at which a parallel setup boost curves crosses the boost curve of a sequential setup, i.e. it's the point where parallel catches up and overtakes the boost pressure generated by the sequential setup. This is, as ever, on a boggo BPU car converted to parallel, and not one with a tuned boost controller or anything else

I type all that and you pick holes

Oh, and I hate flying quite a lot, but one day maybe I'll take you up on that offer though (although me and economy class legroom standards don't easily mix)

-Ian

What do you mean by spin up at 3500rpm Ian? Do you mean starts to make positive boost then?

 

Mine make positive boost around 2800-2900rpm.

 

ps. Oasis are now doing one way budget flights UK to HK from £75, get yourself out here and you're welcome to have a drive. You could also map an EMU for me whilst you're here

 

http://www.oasishongkong.com/gb/en/home.aspx

I agree, mine will make 1bar by 3,500 rpm, obviously gear selection plays a big part.