Paralell or sequential

Am soon to be having 650cc injectors, 264 cams and emanage fitted. Will be keeping the stock tubbies for now ( until saved enough for single turbo).

Would i be better switching them to paralell mode, or leave them in sequential mode?

Thanks

sorry to but in on your post.

what are the advantages of running them paralell apose to sequential

I hate parallel (true twin), there's too much lag (don't let Paul K read this), nothing until 4k then BANG the rear wheels spin in pretty much any gear!!

Advantages are more boost therefore more power at high revs, but disadvantages are NO power at low revs, and annoying lag. Bit like a big single then!!

If you look at the torque graphs side by side, you'll see the sequential has a hump of torque at low revs, then after 4K a bigger hump.

The 'parallel' graph has just the second hump.

Stick with the sequential system or you'll have a really PITA to map. And you're less likely to be happy with the fueling if you're fighting the stock ECU like this.

I know obviously a single goes against the sequential programming in the ECU but it's a completely different map anyway....

I found true-twin awful, and I can't see how it can give you *more* boost than you could get in sequential?!

I found true-twin awful, and I can't see how it can give you *more* boost than you could get in sequential?!

Maybe cause it's less controlled than the sequentials!! Maybe it's cause the first turbo doesn't run at the same pressure as the 2nd one in sequential mode

I was on true twin (full de-cat) - Never going back to it purely because the car becomes way too loud! Motorway driving becomes unbearable. Even at Idle - It's much louder, a horrible sound. Don't know how to descibe the sound but I didn't like it.

Stick with the sequential system or you'll have a really PITA to map. And you're less likely to be happy with the fueling if you're fighting the stock ECU like this.

 

I know obviously a single goes against the sequential programming in the ECU but it's a completely different map anyway....

I would have thought it would have been easier to map in paralell as you wouldnt have to worry about the transistion between the two turbos???

Or am i talking bollox!!!!

i hated TTC too, car sounded like there was a cat (feline type) stuck in the exhaust!

would you get a better 1/4 mile time in Paralell as the rpm will always be above 4,000 (apart from 1st gear unless you managed a good start) i.e. taking advantage of the higher boost compared to seq above 4,000 rpm.

anyone tried both down the drag strip on the same day ?

I would have thought it would have been easier to map in paralell as you wouldnt have to worry about the transistion between the two turbos???

 

Or am i talking bollox!!!!

Nah, cause it's the stock ECU you're trying to fool...the stock ECU is only mapped for the sequential system - it dumps in extra fuel when it's expecting the 1st turbo and extra timiing etc...you're fighting this when you go to map it for a single.

With carrying on in sequestial mode you could conceivably(sp?) carry on with just the Global correction factor, but I don't think this would work completely, esp if you're using more than stock boost.

would you get a better 1/4 mile time in Paralell as the rpm will always be above 4,000 (apart from 1st gear unless you managed a good start) i.e. taking advantage of the higher boost compared to seq above 4,000 rpm.

 

anyone tried both down the drag strip on the same day ?

I think that statement is wrong. Above 4,000rpm both turbo's are working the same, together whether its in Seq mode or TT mode. The only adv you could gain is if you removed the plumbing for the sequential system and had independent feeds to the two turbos.

Nah, cause it's the stock ECU you're trying to fool...the stock ECU is only mapped for the sequential system - it dumps in extra fuel when it's expecting the 1st turbo and extra timiing etc...you're fighting this when you go to map it for a single.

 

With carrying on in sequestial mode you could conceivably(sp?) carry on with just the Global correction factor, but I don't think this would work completely, esp if you're using more than stock boost.

Cheers for clearing that up Alex. It shall be mapped by Ian C, so hopefully he shoulnt have too many problems sorting it.

I think that statement is wrong. Above 4,000rpm both turbo's are working the same, together whether its in Seq mode or TT mode. The only adv you could gain is if you removed the plumbing for the sequential system and had independent feeds to the two turbos.

Thats what i thought but someone told me different. So yes, surely all your doing is removing the first hump on the graph, the second will remain the same as both tubs are doing the same thing as in the seq mode and overall bhp will not change.....if you get my drift

I've been running mine in parallel for over 5 years now and have similar mods to you Smarty. I was advised to go to parallel by my tuners here (HKS pro dealer) who said that it was easier to map the e-manage and extract more power with the turbos running in parallel.

I much prefer the smoother power delivery of the parallel setup, see dyno graph in link below in my sig.

How long have you had your stock tubbies at 1.25bar?

How long have you had your stock tubbies at 1.25bar?

Exactly the same amount of time, because I had one of the stock turbos blow on the dyno run when the e-manage was originally being mapped.

I had 2 new stock turbos fitted and car mapped, that was over 5 years ago, maybe 6 years now.

heckler couldnt decide this either so he's got a lil button that he presses every now and then to switch between the two, dont ask me how it works tho, all i no is his car is like warp speed 9

I presume that at about 3800 rpms the ECU alters the timing or something to allow for the second turbo coming online. Is that why people say its harder to map around this area???

Hi all

I saved out someone's dyno plot once of a parallel conversion. I've attached an annotated version which shows exactly what goes on compared to sequential mode.

You can see the boost pressure curve of both modes of operation. Sequential absolutely kicks the arse of parallel up to about 3350rpm. Then, parallel gets up to 1 bar by 3500rpm, therefore being better for 150rpm. After that, and this is the traction-breaking moment that makes parallel mode *seem* more powerful, there is a really nasty boost spike to 1.3bar - scary when the boost pressure is supposed to be 1.0bar. This lasts for 400rpm before the wastegate opens - the wastegate isn't used until about 3900rpm because the stock ECU doesn't need it to control boost until then - as far as it's concerned, the EGBV controls boost until then.

As you can see, by 4000rpm the wastegate has dragged things back under control and the boost pressure, and therefore power, is exactly the same as sequential mode No higher boost, no magic increase in performance, nothing.

So, parallel gives you:

150rpm (count 'em) of safe higher boost than sequential mode

400 rpm of scary boost spike (the higher your target boost the higher this spike will get as it's basically no wastegate control )

A *lot* less power under 3350rpm

No difference above 4000rpm

Hmmm. You can use parallel if you want but I think it's rubbish

-Ian

Thanks for that Ian. Was interesting seeing the difference between the two setups on a graph.

I will stick with sequential operation me thinks, dont want no nasty spikes causing me grief.

Cheers all

The graphs I've got say a similar story

Cheers John

Also if it's a wired one like mine it makes your vsv rattle like a bastard when on overrun!!!

Mine now rattles anyway after using ETTC a total of 3 times!!!