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The mkiv Supra Owners Club

Sequential vs TTC


Paul Laing

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Ian, give it a try. It's a 15 minute job. IMO, you really don't lose very much low down.

You may lose boost for about 500 rpm, but that's really about it. You get to maximum boost about 500 rpm earlier too.

 

Steve, it really is a simple job. If you don't like it, just switch it off. It's very managable in John's auto. I can't see any reason for concern about engine safety with this mod. You don't get more boost or power, just smoother power delivery slightly earlier in the rev-range.

 

If nothing else, your car sounds throatier at idle and low rpm :innocent:

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Plus i think its MUCH better for turbo 2 as it isnt 'jump'started at 4500rpm , thus you can run higher boost safer (fueling permitting) and the biggest point for me im fed up with kicking the car down and no 2nd turbo then a second later there it is (lovely on some overtakes ) with ttc you know its gonna be there.

Dude:flame Dev

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i was in ttc mode for a while, gone back to sequential now. tried it on dragstrip to see what its like on times. 1st 3 runs in ttc mode netted 2.6 60 foots and 13.7 1/4 which was crap, seemed to take a while for both turbos to come online then went mad

put back to sequential and got 13.059@111mph

got same sort of trap speeds but worse times.

as soon as i put it back in sequential i got my times down. after blowing vaccum pipes off. they both are good i think. my torque convertor is getting fitted now. should be picking it up today and going to drag strip next sunday to see what difference it makes.

 

do like the ttc mode though. put your fut down and car goes mad and squirms about a bit. seems more powerfull somehow

 

matt can you do me the ETTC mode too?

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So, if I understand this correctly, ETTC allows you to switch back and forth between the two modes just using a switch? Also, TTC is more economical?

 

So that means when I'm pootling along in traffic at 15-50mph (say), I could have it in TTC for fuel economy....then if I want more low end umph on the open road, I could switch instantly to sequential? If it does no harm to your engine, then that seems fantastic. Plus another button in the cockpit!

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Originally posted by Tannhauser

So, if I understand this correctly, ETTC allows you to switch back and forth between the two modes just using a switch? Also, TTC is more economical?

 

So that means when I'm pootling along in traffic at 15-50mph (say), I could have it in TTC for fuel economy....then if I want more low end umph on the open road, I could switch instantly to sequential? If it does no harm to your engine, then that seems fantastic. Plus another button in the cockpit!

 

It's only more economical in and around town because you don't get any (or at least not as much) boost when nipping around, hence the ECU doesn't have to pump in as much fuel. It's not a case of it miraculously makes the whole engine more efficient.

 

I would have thought you'd want the sequential system for round town, that low down grunt is what it was built for...

 

Also bear in mind that your ECU thinks 3500 to 4000rpm is time for prespool and bringing in the second turbo, so hitting 1.3bar of boost there when it's expecting to be generating 0.7 to 0.8 may be worth thinking about.

 

-Ian

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Ian

the worst part of the seq. is for me the inconsitancy no2 on kickdown and it isnt just my car loads of others have the same thing , on mine i have to lift off and stamp the throttle if no2 is not there , with ttc you KNOW its gonna be there and there is much less risk of the 2nd turbo leaving via the exhaust at high boost levels , with ETTC you can have the best of both worlds :thumbs:

 

Dude

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Originally posted by Ian C

It's only more economical in and around town because you don't get any (or at least not as much) boost when nipping around, hence the ECU doesn't have to pump in as much fuel. It's not a case of it miraculously makes the whole engine more efficient.

 

Agreed, it only makes about an extra 20 miles out of a full tank, and that obviously depends on how you drive...

Also bear in mind that your ECU thinks 3500 to 4000rpm is time for prespool and bringing in the second turbo, so hitting 1.3bar of boost there when it's expecting to be generating 0.7 to 0.8 may be worth thinking about.

 

Is the ECU actually programmed in this way? - If so, surely if turbo 2 doesn't come on line at 4000rpm, (through some kind of fault that seems to be getting more common), then I'd have thought the ecu would try chucking in more fuel expecting there to be a much higher intake pressure.

 

I was under the impression the ecu compensates increased fuelling as the intake pressure rises... :conf: Regardless of rpm, (to a degree).

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Dude - I see your point, but having a) a manual box and b) no problems with the sequential operation so far, I'll stick to sequential :)

 

Matt - the ECU will have an open-loop fuel map based on many variables, but we don't know the 'envelope' of this map. It may not have any mappings for 1.3 bar at 3500rpm, it might be clipping at say 0.9bar as Toyota never figured the system could go 'wrong' enough to generate more boost than that so low down the rev range. Does that make sense?

 

-Ian

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Originally posted by Matt Harwood

I was under the impression the ecu compensates increased fuelling as the intake pressure rises... :conf: Regardless of rpm, (to a degree).

 

Same here. I thought that the ECU through in the correct fueling depending on the throttle position, air flow, boost pressure etc.. upto what ever the limitations of the map is.? No?! :conf:

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You're right, but what Ian is saying is that, in the same way that they never bothered mapping the car for 2.5 bar at the top of the revrange cos there was no way it would ever get there; Toyota may not have mapped the car up as far as 1.3 bar at 3500rpm because the standard turbo setup would never have delivered it.

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I can see what your saying. I've only got my EGT gauge to go by, but it runs cooler cruising at about 4000rpm in TTC than it does in sequential by about 50 degrees. (Gauge readings only - Taken in 6th gear... On a private runway of course).

It doesnt make any difference at higher or lower rpm... Only around 4000 for some reason - Guessing it's something to do with the changeover point that Terry was talking about some time ago...

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I've got the E-TTC mod, and while I have it in sequential mode 90% of the time, I like to siwtch it over to TT when I'm driving past school kids/ yoofs/ bus stop queues or down crowded high streets, cos it sounds so loud, especially driving slowly in traffic in 1st, and just holding the gear. Just a shame I can't hear it from the outside...

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Sequential operation is a PITA if you are at BPU++ and running 98 Oct gas, as the seq system cant deal very well with high boost coming in a bang at 4k RPM. The power curve is very erratic at the change over esp if your just crusing at 3500 /4500 rpm. The more you modify your car the worse the seq system works! I personally am going with the TTC immediately. Im sure the power can be put down better on the road also should be a lot more smoother !:) will post my opinion soon!:cool:

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