Which is the best engine to go with ITB?

As for the gains of ITBs on standardish engines has anyone installed standalone first and remapped. Then fitted the ITBs and remapped again to see the difference in power? Id be surprised if much peak hp is gained to deal with the loss of torque.

 

Who cares about peak power. It is all about response with ITBs or rapid time to peak torque.

 

I don't know of any examples of that, but others might chime in. Thing is, there are lots of variables, so if someone gained, or made no gains, it could be down to a lot of factors - for example:

- Better/worse map the 2nd time
- Solved another problem along the way and got gains as a result
- Wrong size of ITB's / injectors / other hardware

If it's for a fast road or track day engine that gets used on the road, personally I'd start off with a standard plenum setup, and see if you're happy with the results. There are some very capable track cars running standard or standard-ish engine hardware (e.g. VW_Singh's Mk1, SteveR's & Nige P's Mk2s). You might get a better result from spending money on developing the chassis, or on a better gearbox.

 

What do you mean by rapid time to peak torque?

Im just saying is it worth spending the money on converting the engine to ITBs rather than cams and keeping a plenum.

 

In short, on a standard engine, no.

 

Personally i wouldn’t bother with ITB’s on a road car. There are too many dissadvantages. For one, with the power being talked about in this thread they won’t even be 70% open for full power, therefor the ECU fuel mapping will need to be re-mapped to condense it into about of the mapping sites. This also means that feathering the throttle to get the most out of the engine at normal revs will be hard work. This is maybe the reason for the percieved loss of low-end torque with ITB's....

People say the throttle response is better. Im my experience it’s mostly down to the fact that you’re effectively flooring the throttle at an earlier opening position, which be equally well achieved with an larger single throttle. I had this on my mk1 Golf, i fitted a bigger Audi TB, which seemed to react better. However, when i looked into it properly, I was only flooring it early so the throttle action was actually condensed into less throttle displacement. I put the original TB back on it in the end.

Better throttle response isn’t really needed anyway IMO, as most electronic ECU’s can’t even keep up with the opening action of a single standard throttle. Thus most cars give a weak mixture momentarily on snap throttle activations.

If there were gains to be had, the no expense spared 911 GT3 engine would have them, especially given its longer than normal inlet tract length.

 

aye it is odd that ferraris and lambos tend to use just 2 throttle plates whereas M series BMWs are or were on ITBs.

 

Different type of customer/market maybe.

 

different type of customer, but you'd think it'd be the supercars that most closely followed f1 engine practice, maybe these days with all the variable geometry intakes there is more to be gained under the curve with the plenam manifolds than there is in peak with ITB

 

I would expect that it is easier for these manufactures to control emissions through the use of drive by wire and just two throttle bodies. It would get slighty trickier when you are ITB'ed on V8 V12's.

Again the ECU will on modern engines is programmed for emmisions so has a delay as it gradually increases throttle opening and fueling. SEM's can be calibrated so that fueling with snap throttle openings is almost instantaneous, you setup so they react off the TPS and can increase there responce time to suit your driving prefferences.

The F430 scuderia puts out around 116bhp per litre, the 599 GTO is 110bhp per litre, F360 challenge stradale 118bhp per litre. Maybe this is not enough for them to warrent ITB's, as the VAG motorsporty engines on Chris's table thread that run ITB's push out 140bhp per litre and 155bhp per litre for the last Audi A4 BTCC engine. VAG 16v's running 220bhp on standard (worked on) plenums are putting out 110bhp per litre and the head is incomparison a cr*p design .

 

I agree...
Emissions, road manners, cold idle etc...and with things like the 911s running 3 stage cam phasing and 2 stage inlet manifold switching, it makes you wonder if the torque gains lower down are preferred to a potential gain in power up top?

 

I also think it s to cut the cost down
They could manage some sort of drive by wire ITB
and synchronise each of them with some clever linkage
However like it s been said earlier their specific output is not that incredible
Now if you start to play with them they could be different animals

 

Smudge, do you know how the oe plenum intakes are modified, or can encourage someone else to enlighten us please?

 

Go on then do tell.

I take it the "engine builder" was Grant

Should be good for a laugh what his cost for that engine would be .

I paid around 2500 for the first set up 2l bottom end light flywheel/clutch flowed head cams throttle bodies custom manifold mapped etc etc.

When i say i paid 2500 i swapped the engine build for a Corrado which i was selling for 3500 at the time, i got the engine + 1000 back.

Then i had the Arrow rods/JE pistons remap, cant remember what that cost was but think it was around 1600

Last thing was a top end refresh, had uprated springs fitted at that time with ti caps changed the throttle bodies/pipes and another remap, About another 1600

So about 5700-6000 but could have saved a lot if it was done in one shot.

I have been told that i must have spent 15k to build that engine

Things that went wrong with it.

Split the manifold when an engine mount went at the PVW shoot out
Crack in the block where the gearbox bolts to the engine at the rear, god knows how that happened (it wasnt connected to the problem above as it was more than 12 months on)
Then the valve let go which meant a full rebuild.

New head
Valves
Block
Pistons
etc

So thats pretty much the life of my old 20v engine as far as i can remember and after that i sold it before i got round to running it in again.

Chris shame i didnt get chance to catch up again at the track the other week it would have been good to get a lap in your new racer.

 

Direct from the horses mouth, good update

 

Just done 150 miles this afternoon arround York with another High Spec 16v on TB's first time i had revved the engine past 5k.

The full engine build cost 5500 with nearly all the work done by myself which saved alot of money, i would say it was worth every penny.

The Engine was built to the spec i started out with so all was done in one go which saved money, like MAD20V said best to do it all in one gone.

at the end of the day its all down to what you want out of the engine and build it on that spec. The expensive part is were people change their minds half way through the build.

 

That's not bad Graham, for what was there and how well it went. I guess the rebuild stuck another healthy slice on top of it, but it's not as much as I expected! John Read FTW!

Indeed, but great to see catch you out there just in passing. Just one of those places you 'bump into people you know'

 

Your not wrong about the rebuild, but John did do it at cost (well thats what he said lol)

TBH the original build was very cheap for what was done as he also supplied both the engines that got used. I take it he wanted to use the car as a demo for his engine building but in the end stuck to more of the race car engines.

Also to that cost you could add another 3000 for gearbox rebuild with diff and MS final drive custom rad and some bling pipes etc.

But im sure you all knew that.

 

Hi Mad 20v,
So what was the block that got used in the build. ALT?

 

Went to the scrappy yesterday and N/A 20v's are ripe for the picking. I counted 5, one of which was in a Seat mounted the right way for golfs with downpipe and inlets etc. Probably walk away with a complete setup for around 200-300.

Gurds