# 1.8t with ITB's, COMMON?



## Truckinduc (Apr 24, 2011)

*1.8t with ITB's*

Hi everyone. 

Soon Ill be building an AEB intake manifold. Ill be running a Borg Warner EFR 6758 Twin scroll.. equal length tubular manifold. Im going for quick spool over max hp since this will be a road race car. I know ITBs can drasticly improve throttle response so im seriously considering building a 1 off set for my manifold. It will be a lot of work designing them and actually making them so Id like to make sure its worth doing. The plenum itself will be a center entrance dual plenum design. Intercooler will be mounted horizontal directly in front of the engine with the shortest air path possible. Radiator will be in the trunk. 

So has anyone seen this done? Think Its a good idea? worth the effort?


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## G60 Carat (May 14, 2004)

Hmm Curious,

I'm not 100% sure how much faster the response time will be vs a well designed SRI, and carefully sized, well thought out intercooler/pipe layout. Corky bell talks about air velocity of IC pipes vs the point they become a restriction in his book. It's really a balance of trying to keep velocity up, but restriction down. If you go along the thought of "less restriction, less restriction is everything!" You end up with a lot of power on a dyno sheet to show your friends, but low-mid rpm power and part throttle power will suffer. Not so important on a drag car or dyno queen, but very *very* important factors on a road race car. 

However I do know the SR20DET used it in the GTI-R so there must be something there. Nissan guys say it gives a flatter mid range, and slightly faster spool time. 

In to see where it goes for sure! :thumbup:


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## CorrieG60 (Jan 18, 2004)

It is very possible, just a PITA to get the tuning right...
http://www.hulsenturbotuning.nl/projecten/vw-projecten/vw-golf2-20l-20v-bi-turbo-635pk-2008.html


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## Truckinduc (Apr 24, 2011)

G60 Carat said:


> Hmm Curious,
> 
> I'm not 100% sure how much faster the response time will be vs a well designed SRI, and carefully sized, well thought out intercooler/pipe layout. Corky bell talks about air velocity of IC pipes vs the point they become a restriction in his book. It's really a balance of trying to keep velocity up, but restriction down. If you go along the thought of "less restriction, less restriction is everything!" You end up with a lot of power on a dyno sheet to show your friends, but low-mid rpm power and part throttle power will suffer. Not so important on a drag car or dyno queen, but very *very* important factors on a road race car.
> 
> ...





CorrieG60 said:


> It is very possible, just a PITA to get the tuning right...
> http://www.hulsenturbotuning.nl/projecten/vw-projecten/vw-golf2-20l-20v-bi-turbo-635pk-2008.html



Thanks for the response guys, I was beginning to think no one would touch this subject. 

I know how important velocity VS restriction is. This car will be purpose built for usable midrange power And quick low rpm spool. Autocross - trackday - time attack. The decision to move the radiator to the rear and horizontally mount the intercooler is to minimize piping volume and therefore minimize pressure drop - lag. The cold side intercooler tank will be directly under the intake manifold and feed straight up into the manifold, approximately 14" total. The turbo will mount to the right of the cylinder head above the transmission, approx. 20" of pipe to the intercooler. I have not decided on an actual intercooler core yet. The hope is for the engine to produce 400 to 450 crank hp. The intercooler will be sized appropriately. 

All this is true regardless if i use one throttle body or 4. I can make the throttle body’s from scratch, that’s no problem. The major issue Ill have will be tuning, as I am 95% in the dark on the matter. The entire point of individual throttle body’s would be to pressurize the plenum during short throttle closings like gear shifts. When the throttle plates close the pressure backs up in the plenum momentarily until the plates re open (depending on how quick i can shift). The idea would be to gain instant positive pressure instead of waiting for the relatively high volume of the plenum to build back up to full boost. The effect would be maximized if I did not use a blow off valve (like alot of rally and hill climb cars), But I cant afford the risk of destroying the bearings of a 2000$ turbo due to thrust loading of compressor surge. 

Id love to hear your thoughts on this subject.


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## Truckinduc (Apr 24, 2011)

Here is the start of the plenum backing plate. It will be 2 piece bolt together style.


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## Truckinduc (Apr 24, 2011)

This is the last intercooler setup I built where efficiency and minimizing pressure drop were of top priority.


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## Truckinduc (Apr 24, 2011)




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## Truckinduc (Apr 24, 2011)

got a little bit more work done on the plenum


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## slowgti (Jul 15, 2003)

Have you found a set if itb's yet? Looks awesome so far!


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## Truckinduc (Apr 24, 2011)

[SUP][/SUP]


slowgti said:


> Have you found a set if itb's yet? Looks awesome so far!


I planned on making them not buying them


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## G60 Carat (May 14, 2004)

On the topic of BOV's since several, like Greddy RS are adjustable. Could you not dial it in to vent just enough to keep the turbo safe, but save you the spool up time?


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## Truckinduc (Apr 24, 2011)

G60 Carat said:


> On the topic of BOV's since several, like Greddy RS are adjustable. Could you not dial it in to vent just enough to keep the turbo safe, but save you the spool up time?


The turbo I'm running, EFR 6857 has a built in diverter that basically does that. The air that escapes actually hits the compressor wheel to keep it spooled, pretty trick. 

I guess it would be difficult to determine what pressure would keep the turbo "safe"


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## Truckinduc (Apr 24, 2011)

Plenum plate is about 90% done. Just need to drill it and give it an O ring seal. Then I get to decide to build the rest of the plenum from aluminum or carbon fiber. 



















And cut some out of the back side to shed some weight


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## G60 Carat (May 14, 2004)

Holy,

This might just be the sleeper thread of the year! :thumbup:


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## slowgti (Jul 15, 2003)

Looking good. Have you sized the throttle blades yet? Seems like you would want them slightly larger than the runner cross section to make up for the volume of the shaft and blade.


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## Truckinduc (Apr 24, 2011)

slowgti said:


> Looking good. Have you sized the throttle blades yet? Seems like you would want them slightly larger than the runner cross section to make up for the volume of the shaft and blade.


Im staying single TB right now for tuning simplicity. I am building a carbon plenum though.


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## Truckinduc (Apr 24, 2011)




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## Truckinduc (Apr 24, 2011)

Well I finished it up by adding the bolt holes and o ring slot. Now all thats left is to weld it to the runners.


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## leebro61 (Nov 7, 2001)

Your fabrication/machining skills are impressive!

I did a CFD study a while back on runner inlet radius/profile shaping that I think would be applicable here. I'll have to finish that up and share at some point.

For what it's worth, my opinion is that you made the right choice with a single throttle body. I'm sure you are definitely capable of making ITBs happen, but in a turbocharged car I don't think you'd see the same benefits (at least relative to the additional effort). :thumbup::thumbup:


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## Truckinduc (Apr 24, 2011)

leebro61 said:


> Your fabrication/machining skills are impressive!
> 
> I did a CFD study a while back on runner inlet radius/profile shaping that I think would be applicable here. I'll have to finish that up and share at some point.
> 
> For what it's worth, my opinion is that you made the right choice with a single throttle body. I'm sure you are definitely capable of making ITBs happen, but in a turbocharged car I don't think you'd see the same benefits (at least relative to the additional effort). :thumbup::thumbup:


Thanks. I'd love to hear what you think about my design. 

The runners open up into a .5" radius that blend into a .25" radius.


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## slowgti (Jul 15, 2003)

leebro61 said:


> Your fabrication/machining skills are impressive!
> 
> I did a CFD study a while back on runner inlet radius/profile shaping that I think would be applicable here. I'll have to finish that up and share at some point.
> 
> For what it's worth, my opinion is that you made the right choice with a single throttle body. I'm sure you are definitely capable of making ITBs happen, but in a turbocharged car I don't think you'd see the same benefits (at least relative to the additional effort). :thumbup::thumbup:


Very curious as well. Is there anyway you can play with the surface finish and see how that affects flow?


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## Truckinduc (Apr 24, 2011)

went ahead and made the plenum flange. This one is for a sheetmetal plenum. I havent 100% decided on carbon fiber for the plenum yet, but If i do Ill make another flange to suit it. 










its hard to see but the inner wall has a radius to it










and an artsy fartsy photo i took with instagram


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## leebro61 (Nov 7, 2001)

Truckinduc said:


> Thanks. I'd love to hear what you think about my design.
> 
> The runners open up into a .5" radius that blend into a .25" radius.


If i get home at a reasonable hour tonight i will host some pics and share my conclusions from my quick study.


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## leebro61 (Nov 7, 2001)

slowgti said:


> Very curious as well. Is there anyway you can play with the surface finish and see how that affects flow?


Yes and no (although it's more of a no than a yes  ). I'll start with the "no", then work my way to the "yes". 

In CFD we discretize (sub-divide) the physical geometry into small cells where we solve continuum equations for flow field properties. The cells are typically much, much larger in the streamwise direction than whatever geometric variations you would normally expect to see because of surface finish; so in a way the CFD would not even know that the surface imperfections were there. Here is an example below. 



The solid black line is a NACA airfoil that is being gridded. The equation of that line is a smooth, continuous shape. The CFD grid of that shape would look similar to the red or the blue line(s)... which are just clusters of points that the code would ~interpret as being connected by straight lines (pending the order of accuracy with which the code computes surface curvature), which in reality is of course not the case. If the variation due to surface finish is smaller than the distance between the grid points (which it almost certainly would be), it would be neglected in the computation. I can elaborate if this is still unclear.

Now, for the "yes" answer. Most CFD turbulence models solve equations for both the turbulent kinetic energy and one of either the turbulent dissipation rate or the specific turbulent dissipation rate. Some studies have shown that you can emulate surface roughness effects by specifying particular values of the specific dissipation rate along solid, viscous surfaces. I don't have any experience with that, so I can't comment on it's success first hand.

I can say that in most industries the effect of surface finish is measured experimentally. Once you get to "high enough" velocities and reasonable surfaces finishes things quickly become "hydraulically smooth", meaning surface roughness effects stop being important.


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## leebro61 (Nov 7, 2001)

So, now on to my "study". Let me preface this by explaining my purpose behind the work. I have been writing, developing and validating my own CFD code for the past few years. I use the code for automotive design work and to further my understanding of CFD/aerodynamics (which is also my full time profession). I am gearing up to design a new intake manifold for our company (JDL Auto Design) and in doing so I wanted to run test cases through my code that I could compare back against "known" data. One really well validated case is pressure loss vs. entrance radius/pipe diameter [see reference below, or find a similar plot in ANY fluid mechanics text book]. 










So, I created grids and analyzed flow for a constant radius inlet of 0.090", 0.188", 0.375" and 0.750" on a 2.00" diameter pipe. Shown below are contours of velocity magnitude on a scale of 0-150 meters per second. All cases are ran to the same inlet to exit pressure ratio.

0.090" / 2.00" = 0.045



0.188" / 2.00" = 0.094



0.375" / 2.00" = 0.188



0.750" / 2.00" = 0.375



I'll be brief with my explanation of the physics...

Surface static pressure variations are caused by (among other things) local changes in surface curvature. Convex surfaces create low pressure regions/accelerating flows and concave shapes create high(er) pressure regions/decelerating flows. Surface curvature is inversely proportional to radius, so really tight radius inlets have really high surface curvature. This causes the flow to rapidly accelerate to high velocities, which by itself is fine. The problem is, when this curvature is removed, the pressure returns to normal (rises), so the flow must decelerate. If the deceleration is too abrupt, the flow seperates and large pressure losses follow. Two plots follow below:

[1] My CFD results are plotted against three different textbook references I found. You can see that the absolute level of loss is different between the cfd and most of the textbook data. There are many reasons for this. If my inlet and exit domain are different than where the measurements were taken, I may be accounting for additional loss that was not present in the measurements. Or, most likely, the test data was done using a different fluid at a different velocity and viscosity than I simulated, so that can definitely shift the results. MOST IMPORTANTLY, the cfd captures the sharp increase in loss going below a r/d ratio of 0.10. The cfd also recognizes that there is little/no benefit to increasing r/d beyond 0.20. Both of these conclusions agree closely with the data sets I found.




[2] Surface "ideal" Mach Number distributions are plotted for all the cases I ran. You can clearly see that the green and purple dots (0.188" and 0.090") accelerate over a short distance to the highest Mach Numbers and then must decelerate. You can also see that the red and blue dots (0.375" and 0.750") show similar levels of acceleration and peak Mach Number, so based on this it's not surprising that there isn't a benefit between the two radius'.



I typically don't share stuff like this, but I welcome questions for those that are interested... :wave:


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## Truckinduc (Apr 24, 2011)

Well I've been patiently waiting your write up and I must say I wasn't expecting that much. I appreciate the effort you have put into this brief summary of your work. While most of it is over my head, (I'm a mechanical engineering student but math isn't my strong point) I can use this information. I'm using my very limited and crude understanding of aerodynamics and thermodynamics to design this intake manifold, intercooler and exhaust manifold. 

I'd love to hear your opinion on the work I've put into this manifold so far and if you think I'm headed in the right direction. Ill post some rough sketches tomorrow of the plenum design.


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## slowgti (Jul 15, 2003)

leebro61 said:


> So, now on to my "study". Let me preface this by explaining my purpose behind the work. I have been writing, developing and validating my own CFD code for the past few years. I use the code for automotive design work and to further my understanding of CFD/aerodynamics (which is also my full time profession). I am gearing up to design a new intake manifold for our company (JDL Auto Design) and in doing so I wanted to run test cases through my code that I could compare back against "known" data. One really well validated case is pressure loss vs. entrance radius/pipe diameter [see reference below, or find a similar plot in ANY fluid mechanics text book].
> 
> 
> 
> ...


:thumbup: I owe you a beer. Thank you, time to break out the calculator


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## vwking (Dec 14, 2001)

i love your work i want one


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