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Throttle Body Questions

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1,665
Hey guys, I'm a little unsure on this area so have some questions.

The next step in upgrading for me will be an intake manifold and throttle body, I was originally looking at a 70mm RBC with a 70mm throttle body to match like the Skunk2 TB.

But I have heard that with the 70mm versions the car becomes a little 'jumpy' or very sensitive when driving in normal circumstances.

Now my EP3 is a daily driver so I want some gains but I don't want to ruin normal driveability. So first question is should I get the normal RBC manifold and run this with my stock TB? Or is there a TB to match the stock RBC?

I did have a search but I couldn't find the answer, would it be worth using a DC5 TB? Is there any difference between a U.K EP3 TB and a DC5 one (what is the diameter of each)?

Also what is the diameter of the normal RBC manifold?

So far I have an FC Design airbox and scoop, a DC5 manifold with cat and a Fujitsubo Legalis R catback. Next I'm looking at the intake manifold and TB, I'll fit the same time as a map then, but wanting to keep driveability good for everyday use. I may go for some drop in cams in the future after all this too so any advice?

Any help is appreciated guys and gals :D.
 
Standard RBC fits standard TB. DC5 and EP3 are the same AFAIK.

I was hugely disappointed in the power I made on a DC5 mani, RBC and JDM cams. Something like 228 bhp. Admittedly I hadn't ported the manifold so maybe lost a few horses there.

I ended up ditching the dc5 manifold for a japspeed and made another 20bhp. Then had to change the b-pipe to a silenced one to bring the noise back down.

That said, it never sounded better than it did with that set-up (DC5 mani, unsilenced b-pipe, RBC, JDM cams, AEM CAI).
 
Ah cool, I may go for the standard RBC and keep my TB then. I always thought the DC5 TB was slightly larger.

So is the RBC a larger diameter? Or is it just the bigger chamber and longer runners that give it better performance over OEM?

The main reason I went with a DC5 manifold was to retain the cat, options were limited for a manifold with cat, it was either Mugen which was well out of price range, Piper which I was going to go for but spoke to TDI North who said they aren't a massive fan of them and weighing up costs/gains said you may as well stay OEM, so it put me off. Or the DC5 one which a friend was selling cheap (mates rates lol) and it should give a little gain over OEM, I am going to port it out though before fitting.

Also as it's a daily I want to keep it relatively quiet.
 
70mm throttle body gives very little BHP gain for the £££. Not worth the extra £200-300 for maybe a few BHP increase, if you're lucky. Not to mention having to disturb the iacv and throttle potentiometer. Potentially causing further issues and costing more money.
 
Yeah I've read that you may get an extra 3-5bhp but I suppose it wouldn't be needed on a daily driver, especially if it negatively effects daily driving.

So would we say just go for the 'normal' RBC and keep the standard TB? Or is it worth going for the 70mm RBC and standard TB? Or is there no point in going for the 70mm RBC when using the standard TB?

Loads of questions I know but I want to be sure lol.
 
Yeah I was having this discussion with Stevie at Grinspeed and he said that it's just not worth changing the TB. Plus given that some people experience a jumpy throttle response with a 70mm TB that could become boring quickly in traffic.
 
Cool, looks like I'll go for the 'normal' RBC and stick with my OEM TB then. Thanks for all the input guys :D.

So really a 70mm is only suited for track use then and is pointless for a daily driver/fast road use. Or unless you are chasing numbers on a dyno.

I'm not too bothered about figures, for me the driving feel of the car far outweighs a dyno figure bragging right.

In the long term would the set up of: Airbox with scoop, DC5 mani and cat, Fujitsubo catback, and RBC, would it all be O.K with drop in cams? (and a map obviously)
What DIC are worth going for with those other mods? And with cams would it be beneficial to get an upgraded chain and tensioner like the Toda? Or would the OEM be upto the job?

DIC are the last part and probably won't be done for a long time yet but just after info for future reference.
 
Should be fine with cams. I don't think there's much benefit to be had by going with an 'uprated' timing chain but I guess if it's coming off it's worth at least putting a new OEM one on for piece of mind.

Could go with Skunk2 cams or TDi North's own?
 
Wouldn't bother with cams if you're staying DC5 manifold. For you price you're paying you won't see the returns.

I was in the EXACT same boat, wanted to stay road legal, wanted to cam my car. It just doesn't work out.
 
Or even DC5 cams, but if your going to swap them I would be happier with new cams and TDI norths seem to do very well and not read anything bad about them.
Plus they make more power
 
Yeah cams would be last on my list, they would be either JDM, Skunk or TDI's. First will be the RBC and a map to go with the rest and then I'll go from there to see if it is worth swapping out cams.

Seems like I want the same set up as you've had Hazz so thanks for the advice. There aren't many other options for me exhaust manifold wise, I realise that will stay restrictive compared to a 4-2-1 decat, unless anyone knows of a manifold/cat combination that I don't know about that works better than the DC5 one.

It's difficult because I want to keep it road legal and not have the worry come MOT time etc. But surely it should make some sort of increase? And feel better on the road with my planned set up with or without cams?

Also would there be any benefits in larger injectors?/fuel rail?/fuel pump?
 
Mugen manifold and sports cat will be much better, but at a cost!

The piper manifold has the option to either go decat or sports cat,
but have heard mixed reviews about that one, The cat has to be HOT to pass the mot.
But with that option you could get the cat and de-cat section and get it mapped to the catless and swap the section over for mot.
Or just go the catted route.

Other than that im not sure what else is available
 
I don't think you'll be too disappointed with the DC5 mani, standard cams, RBC, intake and exhaust.

I was only disappointed because I was mapped beforehand and only made an extra 5bhp with the RBC and JDM cams.

If you're going from standard ECU to mapped, you'll be chuffed. It's all relative.
 
Mugen manifold and sports cat will be much better, but at a cost!

The piper manifold has the option to either go decat or sports cat,
but have heard mixed reviews about that one, The cat has to be HOT to pass the mot.
But with that option you could get the cat and de-cat section and get it mapped to the catless and swap the section over for mot.
Or just go the catted route.

Other than that im not sure what else is available

Yeah that's it there's not too many options, I would love the Mugen but bank says no lol, I've heard the same about the Piper mixed reviews, I don't want the hassle of swapping the cat/decat section so I'll see what I can do with the DC5 one, I'll bore it out first and I may look into some heat wrap or something.
 
I don't think you'll be too disappointed with the DC5 mani, standard cams, RBC, intake and exhaust.

I was only disappointed because I was mapped beforehand and only made an extra 5bhp with the RBC and JDM cams.

If you're going from standard ECU to mapped, you'll be chuffed. It's all relative.

Ah cool, yeah I plan on fitting it first and then mapping when the RBC is on the same time. Looking forward to it now lol, and seems I'll go for the normal RBC and ditch the idea of a 70mm TB I'll save a little coin too :D.

Did you do anything with injectors/fuelling? Or would this be pointless on the set up too?
 
Nah, you don't need to bother with playing with injectors until you get up around the 270bhp mark. Same with fuel rail, great for bling but pointless at the N/A tuned level.

At 248bhp I still wasn't hitting full duty cycle on the OEM injectors.
 
Nah, you don't need to bother with playing with injectors until you get up around the 270bhp mark. Same with fuel rail, great for bling but pointless at the N/A tuned level.

At 248bhp I still wasn't hitting full duty cycle on the OEM injectors.

I was at 92% on the FN2 with 260bhp 180ftlb which was getting close but not there yet. :)
 
Thanks guys that's good to know looks like I'm re figuring my set up and you have saved me some coin too, so thanks for all the input guys, you've all been a great help! :D.

So I'm going with my FC Design airbox and scoop, DC5 Mani and cat, Fujitsubo catback, normal RBC and K100 map, and see how this goes. Possibly DIC in future.

I'll put the DC5 mani and catback on next as they aren't fitted yet. Just done the big 75k service changed all fluids, oil filter, fuel filter, valve clearances sorted and timing chain etc checked and all is spot on now, also had 4 new tyres fitted.

I want to get new drop links, track rod ends and JDM ARB's, the front to accommodate the DC5 mani hence why I have not fitted the exhaust system yet.

Once I'm happy with that it'll be the RBC and map.

I've also got a new clutch to go in at some point, want a LSD too, bloody list in endless lol but hopefully it'll all be sorted soon! Thanks again guys much appreciated!!!
 
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