Individual Throttle Bodies Vs Plenum And Single Throttle Body

[russandra]

Hi Guys,

 

I am in 2 minds here so bear with me.

 

I am in 2 minds regarding using the EFI hardware ITB's or using a Plenum type manifold with a 80mm or so Throttle body. The engine I am currently building is a L28 stroker with a planned 230HP at the treads.

 

I was told by my Engine builder that the ITB setup will create better off idle throttle response, slightly more HP and a smoother idle. My main question is is it worth the extra $ to go ITB and why is it better to go thst way.

 

I couldnt care less about period looks, loyality to brands or simple answers like I just prefer X. Just want real mechamical facts. Dont bother mentioning Webber carbs or Jenvy cause not interested.

 

As far as cost goes, ITB setup is over $3000 and webbers cost this so I cant care less about the Webber, Mikuni or Dellorto route. The custom Plenum route will cost me around $1500 including machining etc. Only interested in injection. Who caan help? Obviously tuning is on top of this.

[Cozza]

I think only you can answer that question as it is related to a financial cost.

I agree with the points made by your engine builder as to the benefits of itb’s. Depending on volume, length size and any flow restrictions of your proposed plenum, you may gain size mid range torque from a well designed and built plenum.

If it’s ‘worth’ the extra $1500 is up to your bank balance.

I would be guessing your spending in the region $15k for a full stroker engine build with tuning etc. so an extra 10% is only 10%.

I say go for for the itb’s.

 

Edit. Nah, go on the advice of your engine builder.

Edited March 11, 2018 by Cozza

[KatoKid]

ITB's for sure.

 

OEM's put massive time and development into plenums and single throttle body design for torque and efficiency, You don't have the resources so anything you build could be sub optimum...why don't people use the factory EFI plenum ....probably cos its not very good.

[GregTas]

I was initially going to build a NA EFI L28 for my car and did quite a bit of research on throttle body options and decided on these as my preferred. Mainly because they looked quite good and quite a bit cheaper than the other throttle bodies available. 45DCOE bolt pattern and only $337 each in Aus.

 

 

https://www.ebay.com.au/itm/45-DCOE-EFI-throttle-body-injection-fajs-45DCOE-/173172663820?_trksid=p2385738.m4383.l4275.c10

 

For the three throttle bodies, Weber manifold and injectors perhaps about $2200 or so total cost. The difference above a single throttle body option is probably only $1600, so perhaps more reasonable.

Edited March 11, 2018 by GregTas

[d3c0y]

Since the question has been answered and I agree with the first two answers... There is no way that ITB EFI costs the same as a carby setup because of the ancillary devices you need to run it. Sure ITB units themselves are on par with the carbs for cost but there are so many other things you need like a computer, surge tank, high volume pumps, bigger return line etc etc.

 

PS when are you coming to get your Konis?

[russandra]

 

 

PS when are you coming to get your Konis?

 

Will give you a ring this week, most likely on the weekend. Fly home on Tuesday.

[satrat z]

I have had both on my track 260z, I have to agree with some of the replies.    Absolutely the ITB's are the better option if you are chasing max HP.

 

Without knowing what you already have re suitable computer, harness, pumps etc etc, don't under estimate the cost of ITB's to set up properly.

 

 My set up came from EFI hardware and I couldn't have been happier with the service and quality.With needing a new computer to make the most of the ITB's, a new custom wiring harness etc etc there was very little change out of $10k and that was doing the whole installation myself.

 

Previous to the ITB's I had a modified original plenum manifold with an RB30 throttle body.  The off idle smoothness and low down torque was very similar to the ITB's but beyond mid range and into the top end the ITB's were noticeably better.     I had a dyno done with both options and the dyno sheet confirmed the advantage in the later half of the rev range.

 

One of the limitations with the plenum manifold was having to use a relatively mild cam. Too much overlap in the cam causes airflow interference within the Plenum as the next intake valve opens.   This caused a flat spot around 4200rpm.

 

My opinion though, if I wasn't needing high rev performance all the time, like on a track and was using on the road, the plenum manifold and single throttle body was a simple and smooth set up that was about a quarter of the price and performed as well as most triple carbs that I have set up on other L28's for road use.

[gav240z]

I still reckon Triple Mikuni/Solex set up well, simple... not that expensive in grand scheme of things (won't lose value as someone will always want a decent set) and once tuned correctly you shouldn't have to make any adjustments. I love mine, can't rave about them enough!