16V K headed turbo, race engine, need for restrictor
Turbo Mini Forums

As you know from my project thread I am building a "proper" racecar based on a 1970 shell.

The series i am going to compete in is based on kilos/hp calculations. They have set a certain calculated hp amount for different engine set ups. The set ups that may be useful for me is:

1. 16V head, NA, free throttle bodies, 130 hp pr litre
2. 16V head, turbo, 32 mm restrictor, 150 hp pr litre.

My engine has a volume of 1.343 litre, so I would theoretically be allowed to weigh 559 kg's at the finishline with me in with option 1. This is not possible.

However they have set a 650 kg minimum weight for the class. 650 kg is probably where I will end up including driver anyway.

with option 2 I am allowed to weight the same 650 kg. (which should be possible in real life as well)

the series have two races a day, one 7 lap race, and one 30 lap race. (laptimes around 1 minute).

I think they have kind of "forgot" that it might be clever to use a lightweight car with a small volume with a turbo in the rules. all the others use 2 litre engines and above.

Would you guys go turbo, or stay NA?

The way I see it, turbo makes sense, less rpm, so should be more reliable, as well as the option to run two set ups, one for the quick 7 lap race, and one for the 30 lap race where finishing is vital (loads of people fail:))

What I do not really know is what kind of influence the 32 mm restrictor would have?


Sorry for the long winded post, but I really hope to get some discussions started here:)

Edited by miniminor63 on 28th Sep, 2010.

obviously there are many considerations, but the obvious one to me would be the entrance to the turbo surely isn't much more then 32mm. I'll go measure my gt17.

Edit: I've just measured it at 40mm.

Second edit: Do wrc cars not have 34mm restrictor? They make plenty of power and loads of torque.

Edited by minimole23 on 28th Sep, 2010.

32mm square restrictor aloud?

Yes i moved to the darkside

Instagram @jdm_brett

a round 32mm turbo restrictor is a world rally group N requirement. The restrictors are fitted on the inlet side, and yes, certain turbos have an inlet not far off 32mm.

The 32mm restrictor has a theoretical power limit, basicaly the 32mm hole will only flow so much air, and it mainly takes effect at higher rpm when the engine is consuming the most air.

Do the regulations not also say how far from the turbine the restrictor needs to be?

Thanks for the thoughts guys!it is the same as group N restrictor yes. It should be put close to the inlet but no stringent rule on how close.

Edited by miniminor63 on 28th Sep, 2010.

You could get clever and do what Toyota did. I heard that the modified restrictor was so clever that it passed all FIA scrutineering for several events, and wasn't until a changed out turbo unit was inspected by scrutineers on a service stop, that something was thought to be not quite right.

Look at it this way, if it baffled the FIA scrutineers on a world class event, im sure your average club scrutineer wouldnt have a clue

PMSL!!!

How did i not know about this!!

lol.

I don't think the restrictor will be that restrictive for a small engine like ours really, so I do not think I will bother making something like that. Its quite intricate :)

Are anybody able to help me out on how to calculate stuff? How should one calculate what kind of mass air flow will be maximum through the restrictor? Also the pressure relation used when reading compressor maps will no doubt be influenced by this. I guess it will be larger in general, as the pressure on the inlet side will be lower?

well to make 200bhp (150 x 1.343) you'll need 22 lb/min. Depending on what rpm you make this at you'll need around 16 to 20psi boost.

I have no idea how to calculate flow through a restictor.

Fastest 998 mini in the world? 13.05 1/4 mile 106mph

The restrictor will not impose a maximum limit on the flow until the velocity goes supersonic. But it will produce a pressure loss at the compressor inlet that will severly restrict its performance throughout the power range.

You can calculate the pressure loss through the restrictor for a given air flow. The calculations are complex, based on Bernouli, and the loss will vary depending on the discharge coefficient Cd.

Cd will be lowest if you can provide inlet and outlet diffusers as that picture above. Obvioulsy it will be a lot higher with just a hole in a flat plate.

http://en.wikipedia.org/wiki/Venturi_effect

Even if you took the trouble to calculate the head loss, we do not have any data to determine the impact on the compressor.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Thanks Paul!

Would it have any impact on the compressor other than making it work harder due to a larger Pressure relation?

The problem is that the performance of centrifugal machines, like the turbo compressor, are affected once the absolute pressure at the inlet goes below a certain value.

You can liken it to stall in aircraft, although it is a little more complex in nature. The flow of air across the blades is not high enough so the blades do not perform correctly.

So, as well as seeing a higher pressure ratio, the compressor map will assume a different shape.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

hmm, food for thought. Maybe it would be a good idea to go to someone with vast turbo engine and turbo selection knowledge and ask them for turbo selection advice... I am able to read and understand compressor maps, but this adds another dimension...

likely wont be cheap though...

okay, here is the current plan (funds permitting):

-K16V 1200 head with thin valve stems.
-at least 11:1 compression or there abouts.
-Comp turbo custom turbo charger with a 32 mm restrictor.
-either stay with the cams I have, or maybe go with a slightly milder inlet cam.
-E85

Power goal is at least 230 hp, max 7500-8000 rpm.

Are you sure that the improved efficiency of the higher CR is going to offset the lower calorific value of the E85 ????

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

As I wrote in another post:

Edited by miniminor63 on 30th Sep, 2010.

I am sceptical until I've done the sums.

Depends on what AFR you can run on E85.

E85 only has around 2/3 the calorific value of petrol, so if you will need to run AFRs below 10:1 to compensate.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

stochiometric AFR for E85 is 9.75

Well, apparently E85 gives maximum power at an AFR of about 7:1, so you should be on to winner.

Edited by Paul S on 30th Sep, 2010.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

lol, you beat me to it!

Edited by miniminor63 on 30th Sep, 2010.

Edited by robert on 30th Sep, 2010.

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

when talking about how rich the fueling should be with E85 it is easier to understand if you use Lambda instead. One reason why VEMS uses a Lambda target table instead of an AFR target table (lots of Sweeds use E85 and lots of Sweeds use VEMS). Its only the VE table that then changes, as the fuel demand is much higher. You will need to check the demand on your injectors.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."