Upgrading to throttle bodies on a Fiat/Lancia 16v turbo
Posted: August 10th, 2006, 10:38 pm
Hello all,
I'd like to set up a thread here to discuss converting a single throttle Fiat/Lancia 16v turbo engine into a four single throttle body set up, it's just for me and you to learn from and for ideas and theories to be discussed, I'll start if off here by tellling you what I have learned and what I would like to achieve, please feel free to comment, advise and tell me if you think i am wrong in any particular areas.
The car is a 16v integrale that I use as a test bed for my ideas and as a trackday car in between, it isn't used on the road and when it is finished I would like to compete in it, quite what in I don't know! But I do enjoy driving it hard and have a competitive streak in me.
First of all why Throttle bodies?
Well, the standard 56mm throttle plate on this engine is ideal for up to about 320bhp, after that it becomes restrictive, sure you can get more power whilst still retaining it, but still the fact remains it is causing a restriction. Some people bore out the housing on the Lancia one and fit a larger butterfly (or throttle plate) this is a good move as far as it goes, but go too large and low speed drivability can be difficult, as you can imagine, cracking open a large throttle plate even a tad can let a large amount of air through suddenly, resulting in setting off a bit quicker than you intended (!) and a jerky response. The Fiat (16v turbo) gets around this problem by shrouding the top half of the plate, this means that on part throttle openings only the bottom crescent is used up to a certain angle, then after that the full circle is exposed bit by bit, it's a very clever but simple design and works well:
To sum up: I am looking for more power with good response and controllability. First of all I found a suitable donor for the manifold, it is perfect in a few ways:
1. The bore size is 40mm, this equates well with the inlet valve size of 34.2mm and puts it firmly in ideal circuit/drag car territory, very slightly too large for street/hillclimb/rally, but nothing to worry about, not when I can adjust the total length of the inlet tract to compensate.
2. The flange fits the head spot on. (Almost as if it were made for it )
3. The injector boss is very close to the base, this is perfect for low speed pick up, for higher engine speed the second set of injectors mounted higher up in the Tbs will come into play.
4. It has circular/tubular ends with a recess for the rubber which joins onto the TB, seperate Jenvey SS bodies fit perfectly.
5. The total length of the whole inlet tract also measures up well with recommendations for circuit/drag use, maybe a little short for street/hillclimb/rally but again, it can be lengthened if needed with longer bellmouths.
The downside: It presents itself to the head at completely the wrong angle. I worked out geometrically what I needed, cut it up and had a local fabricator weld it back together again. The angle isn't perfect, but to get it perfectly in line with the ports would mean the Tbs poking through the bonnet. Here's a comparison: Before (lower) and after (upper)
And here's a shot down the bore;
And then up it:
Here's a shot of the Jenvey throttle body:
And finally, a pic of me having a trial fitting to see what it is like for clearance, the timber dummies are dimensionally correct to help see any future problems, I can see one looming, but nothing my saw won't sort out.
Ok, now some awkward questions:
I need to have vacuum take off points fitted for brake servo, Map sensor and idle control valve, these are going to have to come from the Tbs and the manifold, the ICV is pretty much catered for here:
1st question: How exactly does the ICV work, what does it do?
Will the map sensor work ok from 4 joined together points? I have been told it may not be happy at the pulses hitting it, I can dampen the pulses with small bore hose and a small fuel filter, but then this would delay the signal perhaps and make it useless..... (this is my main worry)
Can I take off the vacuum point for the brake servo from just one runner or will this cause an imbalance? (I think maybe not as it is only working on deceleration and will 'lock up' under boost due to the fitment of a one way valve)
Do you think my efforts at improving the inlet manifold angle have made any benefits and could they be improved?
Martin.
P.S. I'd like to perhaps discuss intake plenum design next if that is ok?
I'd like to set up a thread here to discuss converting a single throttle Fiat/Lancia 16v turbo engine into a four single throttle body set up, it's just for me and you to learn from and for ideas and theories to be discussed, I'll start if off here by tellling you what I have learned and what I would like to achieve, please feel free to comment, advise and tell me if you think i am wrong in any particular areas.
The car is a 16v integrale that I use as a test bed for my ideas and as a trackday car in between, it isn't used on the road and when it is finished I would like to compete in it, quite what in I don't know! But I do enjoy driving it hard and have a competitive streak in me.
First of all why Throttle bodies?
Well, the standard 56mm throttle plate on this engine is ideal for up to about 320bhp, after that it becomes restrictive, sure you can get more power whilst still retaining it, but still the fact remains it is causing a restriction. Some people bore out the housing on the Lancia one and fit a larger butterfly (or throttle plate) this is a good move as far as it goes, but go too large and low speed drivability can be difficult, as you can imagine, cracking open a large throttle plate even a tad can let a large amount of air through suddenly, resulting in setting off a bit quicker than you intended (!) and a jerky response. The Fiat (16v turbo) gets around this problem by shrouding the top half of the plate, this means that on part throttle openings only the bottom crescent is used up to a certain angle, then after that the full circle is exposed bit by bit, it's a very clever but simple design and works well:
To sum up: I am looking for more power with good response and controllability. First of all I found a suitable donor for the manifold, it is perfect in a few ways:
1. The bore size is 40mm, this equates well with the inlet valve size of 34.2mm and puts it firmly in ideal circuit/drag car territory, very slightly too large for street/hillclimb/rally, but nothing to worry about, not when I can adjust the total length of the inlet tract to compensate.
2. The flange fits the head spot on. (Almost as if it were made for it )
3. The injector boss is very close to the base, this is perfect for low speed pick up, for higher engine speed the second set of injectors mounted higher up in the Tbs will come into play.
4. It has circular/tubular ends with a recess for the rubber which joins onto the TB, seperate Jenvey SS bodies fit perfectly.
5. The total length of the whole inlet tract also measures up well with recommendations for circuit/drag use, maybe a little short for street/hillclimb/rally but again, it can be lengthened if needed with longer bellmouths.
The downside: It presents itself to the head at completely the wrong angle. I worked out geometrically what I needed, cut it up and had a local fabricator weld it back together again. The angle isn't perfect, but to get it perfectly in line with the ports would mean the Tbs poking through the bonnet. Here's a comparison: Before (lower) and after (upper)
And here's a shot down the bore;
And then up it:
Here's a shot of the Jenvey throttle body:
And finally, a pic of me having a trial fitting to see what it is like for clearance, the timber dummies are dimensionally correct to help see any future problems, I can see one looming, but nothing my saw won't sort out.
Ok, now some awkward questions:
I need to have vacuum take off points fitted for brake servo, Map sensor and idle control valve, these are going to have to come from the Tbs and the manifold, the ICV is pretty much catered for here:
1st question: How exactly does the ICV work, what does it do?
Will the map sensor work ok from 4 joined together points? I have been told it may not be happy at the pulses hitting it, I can dampen the pulses with small bore hose and a small fuel filter, but then this would delay the signal perhaps and make it useless..... (this is my main worry)
Can I take off the vacuum point for the brake servo from just one runner or will this cause an imbalance? (I think maybe not as it is only working on deceleration and will 'lock up' under boost due to the fitment of a one way valve)
Do you think my efforts at improving the inlet manifold angle have made any benefits and could they be improved?
Martin.
P.S. I'd like to perhaps discuss intake plenum design next if that is ok?