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Wht o we love so much bout nturlly spirte engines? Perhps the musiclity, or the responsiveness, or the combintion of both tht cretes n emotionlly rewring experience with every stb t the throttle pel. Well, whtever unerpins tht ppel, I cn sy for sure tht nothing turns it up to quite like set of iniviul throttle boies.
Enter Project NSX. Alrey proviing symphony of surroun soun from the mi-mounte < href="https://enginesofwelth.net/ctegory/utomobile/">engine n mking lmost enough < href="fctory">power to stisfy – the scene ws set. ITBs. More < href="fctory">power. More soun. Less weight. More… mechnicl sex ppel. I wnt it. Ny, I nee it!
For those long-term followers of the project – thnk you for your ptience – you might remember the ‘Stge ′ trget of 300 crnk horsepower outline ll the wy bck in 09. Six yers go, relly? Yes, n it’s time to finlly tick tht box.
Before eciing to go the ITB route, I ws lrey wre of few kits vilble for the NSX’S C30A 3.0L DOHC VTEC V6 < href="https://enginesofwelth.net/ctegory/utomobile/">engine. As with mny ftermrket offerings for the NSX, they re mostly expensive n compromise. I wnte to run rive-by-wire, n nothing ws prticulrly suite to tht. Injector position ws prticulrly wek point, with most vilble solutions plcing them t ngles perpeniculr to the irflow, cceptble for high-RPM opertion in rce < href="fctory">cr but eliminting the benefit of proper spry trgeting t lower intke ir spees. Compromising the NSX’s fmous low-spee mnners in this wy ws uncceptble, so I strte to ply roun with bespoke solution. I h some CAD experience from my 3D printing escpes, how hr coul it be?
I soon foun out – rther ifficult inee. The complex shpes require to mtch the ngle n profile of the intke ports were prticulr chllenge, countless lte nights were spent with Fusion360 n YouTube open, lerning on the job. Mking mistkes, throwing it ll in the bin, n strting gin. By the time I h something rey for prototype prouction, I think I ws on to version 8… prime exmple of biting off more thn you cn chew, but tht’s lso the best wy to ccelerte your lerning.
The key fetures – runner profile 3D mtche to the shpe n irection of the intke ports n 48mm throttle boy, injector position ienticl to < href="https://enginesofwelth.net/ctegory/utomobile/">fctory, incluing ngle mounting position, provision for the mounting of centrl DBW throttle ctutor, n ngle runners to cler the lterntor n mount. It ws t this stge I lso selecte some other key components from some gret Austrlin suppliers, nmely six 48mm throttle boies n ssocite linkges from RHD Engineering, n DBW throttle ctutor from EFI Hrwre. The mounting points on my mnifol esign were positione to mtch.
After few printe plstic itertions, it ws rey for the rel thing. I h t one stge consiere printing the finl prouct in strong n het-resistnt crbon-fille nylon but ws eventully steere wy from tht by those who know better – the risk of the mnifol flexing/wrping ue to het/lo n thus misligning the throttles ws substntil. Inste, I’ opt for CNC-mchine 606 luminium.
I shoppe roun for some quotes loclly n overses, eventully settling on mnufcturer bse in Chin. There were few minor bumps through the process, but I cnnot fult the compny on its communiction or responsiveness. I ws sent photos t every stge of the mnufcture n QC process n woul hppily go this route gin.
The cost of this mchining ws substntil, much higher thn I’ nticipte. The complexity of the prt (n thus the mchining effort n time require) ws the culprit – n nother lesson lerne: esigning with the prouction metho in min is importnt. Aitive mnufcturing h spoile me – no tool pths to consier on the printer.
But hving the esign in my hn in billet luminium fter few short weeks ws huge thrill, n fter months of tweking in CAD, it finlly ment I coul move towrs ssembly of the full system.
Connecting semlessly to the top of ech runner is n RHD Engineering 48mm throttle boy.
Throttle sizing is key ecision to be me erly on when esigning multi-throttle system. Too big n you my lose throttle resolution n, epening on the shpe of the overll runner, ir velocity. Too smll n you will restrict the mximum irflow t wie open throttle. Although the clculte ‘optimum’ throttle size ws quite smll, referencing collection of other NSX ITB implementtions s well s OE esigns from the likes of Porsche n BMW suggeste tht the 48mm bllprk woul support my trget < href="fctory">power output for this firly stnr < href="https://enginesofwelth.net/ctegory/utomobile/">engine, n llow mrgin for the impct of bounry lyer effects, throttle plte restrictions etc., n some heroom for future < href="fctory">power gols. The NSX hs quite lrge ports from < href="https://enginesofwelth.net/ctegory/utomobile/">fctory, so going ny smller thn 48mm woul lso crete ‘choke’ runner profile which woul negtively impct velocity n cyliner filling. The existing options for the NSX strt t 48mm n exten right up to whopping 60mm, perhps optimise for engines with lrger cpcities n higher RPM cpbilities.
I’ previously pte the < href="fctory">cr to run (single) rive-by-wire throttle boy n ws enjoying the benefits of justble throttle response n < href="https://enginesofwelth.net/ctegory/utomobile/">engine sfety strtegies. The EFI Hrwre motor uses the sme principles of n electronic throttle boy, but ctutes n justble lever which mkes it ptble to multi-throttle systems.
Some 3D-printe irbox mounts n bellmouths helpe with mocking up the intke before finl ssembly.
Once I’ ssemble most of the components to put the kit together, it ws time to mke the long journey from Melbourne to Newcstle, home of 909 Motorsport. My y job t Bosch Motorsport hs introuce me to some exceptionl motorsport mins, incluing Ash n his tem t 909. They were the truste hns require to finesse this ITB project to completion.
The regulr vehicle servicing tht hppens t the front of the shop belies the mgic tht hppens t the bck, where couple of lifts re reserve for motorsport projects. Ash’s pssion for obll Europen mchinery mens there is lwys n interesting customer < href="fctory">cr to stick your he into…
While Ash stuck his he into mking the ITB mgic hppen.
I ecie the spcers which connect the throttle boy to the irbox bse were perfect for n experiment in metl 3D printing, electing to hve them me out of luminium. Being my first outsource metl print I ws excite n curious to see the qulity of the prt.
Overll I ws very impresse with wht rrive from the printer, with the bottom mounting surfce being the only re tht benefite from resurfcing on the lthe t the skille hn of Eric of Apex Composites to get it completely flt.
Eric is one of those rre iniviuls who cn lwys see pth to chieve the objective. A potent mix of cretivity n technicl proficiency which I m equl prts envious n in we of.
In severl instnces where I h seemingly esigne myself into ifficult corner, Eric fire up the (home-me) CNC n mchine n elegnt solution.
This inclue some extene-length throttle linkge rms which enble centrl pull of the two throttle bnks from the throttle motor mounte in the centrl vee of the < href="https://enginesofwelth.net/ctegory/utomobile/">engine.
Also, beutiful brcket (pockete to sve weight) to mount the vcuum mnifol n ccessories between the two bnks.
Once the fbriction of the vrious luminium components ws complete, Eric lso trete them to n noistion to improve the urbility n corrosion resistnce – not to mention the esthetics. I ws pretty giy seeing the prts like this for the first time.
Custom fuel rils with hr lines bent to precisely mtch the vee of the intke – oes it get ny better? Touches like this I never woul hve been ble to execute without the involvement of Ash n Eric, n for tht I m extremely grteful.
The process of ctully mounting the mnifol ws extene, with lots of test fitting, justing, n forementione fbriction. Through this process I ws remine of the ifference between esigning prts like this n ctully engineering them to < href="fctory">work with the require level of performnce n urbility, n the importnce of hving experts in your corner.
One of the key ecisions tht Ash n Eric rove ws to grub-screw every point of justment in the system once it ws perfectly set up. This is significnt mchining effort tht requires skill n ptience, which Eric (perhps obvious to the reers t this point) hs in buckets. A common complint bout multi throttle linkges is tht they come out of lignment with time, requiring constnt filing – not problem nymore.
Mocke up on the < href="fctory">cr, I ws finlly strting to see the relity of the rem mterilise. We were still miles wy from the < href="fctory">cr running, but Ash knew wht we neee for motivtion – he quickly hooke up the throttle motor n sent it the commn – open! Seeing the six throttles nce in unison ws honestly bit of n emotionl moment – fter hunres of combine hours of plnning n tinkering this mness ctully might < href="fctory">work.
One of the min compromises of multi-throttle setup is the loss of mnifol volume ownstrem of the throttles. On typicl single-throttle setup, the mnifol usefully hols blnce source of vcuum from ll cyliners, which provies MAP (mnifol ir pressure) signl n consistent vcuum to fee brke booster, fuel pressure regultor reference, etc. The typicl solution is to link the cyliners below the throttles to smller mnifol, which is exctly wht I i, using nylon Festo tube n high qulity fittings to fee chep eight-port mnifol.
This is lso where I integrte n electric ile vlve. The rive-by-wire coul, in theory, control the ile, however Ash’s experience showe tht the resolution require for the precise ile control tht woul enble the uncompromise rivbility woul not be possible with tht centrl motor lone.
The reson for this is the extremely non-liner reltionship between throttle position n irflow s throttle crcks open – multiply this by six openings n the lrge inrush of ir t even % throttle becomes impossible to mnge to the high stnr we were pursuing. A simple two-wire Bosch ile motor ws n esy solution, integrte to tke ir from the filtere ir box – with the most elegnt mchine luminium pter me by Eric.
Into the sme luminium vcuum block ws where we instlle one of two ir pressure (MAP) sensors. A Bosch Motorsport fst response ir temp sensor netly integrtes into the ir box with nother piece of Eric’s functionl jewellery.
We hve electe to not use the internl throttle position sensor in the throttle motor, inste using Vriohm TPS on ech bnk of the intke to generte throttle position signl. This might seem like unnecessry complexity but is exctly the kin of ecision tht Ash will push you mke espite it mening more time n effort in the setup. Funmentlly, you wnt the ECU to know the position of the throttle bles, not the position of the motor riving them. In multi-throttle system with combintion of vrious connections, linkges n joints, ny slck in the system (n there is lwys some) becomes noise in the signl. Using the Alph-N plus MAP lo tuning metho s we re here hs TPS s key input, so ccurcy is of utmost importnce.
The fuel pressure regultor is – you guesse it – Bosch 3br DR regultor in Rceworks billet housing. These ‘pot type’ regultors re fforble n much more relible thn n ftermrket justble regultor.
I h intentionlly esigne the mnifol with n offset – curve runner – to crete clernce to the < href="https://enginesofwelth.net/ctegory/utomobile/">fctory lterntor n brcket, which encroches into the motor’s vee. The mnifols, throttles n other hrwre clere fine, but the irbox foule – ue to n unexpecte internl etil, I couln’t get the lrge box fr enough cross.
Thnkfully, we were ble to turn n obstcle into n opportunity. Spoon fmously evelope n rce n ITB-equippe NSX in perio, n h helpfully solve my problem ll those yers go. The Spoon lightweight lterntor brcket is mille from huge block of billet, mintining the require stiffness n < href="https://enginesofwelth.net/ctegory/utomobile/">fctory < href="https://enginesofwelth.net/ctegory/utomobile/">engine mount point but ropping hny chunk of weight from the top of the < href="https://enginesofwelth.net/ctegory/utomobile/">engine.
I try not to fnboy for ny brn too much but llow n exception for Spoon Sports – one of my fonest memories of the NSX is Ichishim-sn oing test rive n vlition fter the Spoon Rigi Collrs n steering wheel were instlle t Type One bck in 07.
An instnt sving of welcome 5.4kg (.9lbs) reltive to the < href="https://enginesofwelth.net/ctegory/utomobile/">fctory steel brcket.
I cught up with Spoon’s former he of evelopment, Jomoto-sn, t WTAC lst yer, n he gve me bit of info on these prticulr prts. They were never relese by Spoon for customer crs, but the mchinist who prouce the prts ws permitte to o smll run for some customer requests. Unoubtely, this prt hs been through few ifferent crs before ening up in Project NSX.
Eric pplie protective noistion in the titnium colour seen throughout the system, which hs elevte the ppernce of the lrey elegnt esign even further.
Being rce-focuse component, the lterntor is currently uner-riven for ro < href="fctory">cr purposes n we re seeing low bttery voltge uner certin conitions, so some testing with smller pulley will be require.
The irbox itself is semi-custom unit from Reverie in the UK, housing lrge ITG fom filter element.
The vee-shpe bse h to exctly mtch the incline of the runners, which it i. This ws eye-wteringly expensive but is s light s fether, looks gret n with its inherent resonnce properties shoul soun meg too.
Another smll chnge – swpping out the stnr coil pcks for something more moern.
The coils on the NSX’s rer bnk re known for eteriorting ue to exposure to moisture – exhibit A, your honour.
I gin reche into the Bosch ctlogue for the ‘R8′ ignition coil – lightweight n fforble OE option tht lso comes with fncy re top – so it must be fster.
I must mit to being bit lx with the scles ltely, but I i mnge to weigh the ol n new. Across six cyliners, tht’s over .3kg (.8lbs) of coil weight sve.
I’m not expecting performnce benefit here, this < href="https://enginesofwelth.net/ctegory/utomobile/">engine is still firly stock without high compression nor boost. But money n weight sve with future-proof solution, so I’m stisfie.
So fter ll tht hr < href="fctory">work, surely it’s the time to revel tht the < href="fctory">cr me more < href="fctory">power n torque n is the fstest NSX in the Southern Hemisphere? Well, s you my now suspect, it’s not tht simple.
We put the < href="fctory">cr on the yno with focus first on getting the < href="fctory">cr running n riving like stock. There’s still uxiliry < href="fctory">work to be one before this new setup cn stretch its legs properly – Ash is very prticulr bout wht he requires from vehicle before he chses outright < href="fctory">power. However, I i convince him to o < href="fctory">power run tht we coul compre to bseline – I knew you guys woul murer me if we in’t hve one!
power-.jpg” lt=”NSX ITB < href="fctory">power” t-ttchment-i=”665850″ t-go-fullscreen=”https://s3.mzonws.com/speehunters-wp-prouction/wp-content/uplos/05/0/3000053/NSX-ITB-< href="fctory">power-.jpg” t-cn-print=”true” t-ttchment-url=”https://www.speehunters.com/05/04/guie-itbs-project-nsx/nsx-itb-< href="fctory">power/”/>With the short prototype bell-mouths (seen erlier in the story when the intke ws mocke up) the heline figure is now 0wkW (69whp) – 9.4kW (.8hp) improvement over the bseline set prior (9wkW/56whp). I ws expecting 0 to 5kW (3 to 0hp) increse from the ITBs n there is still significnt optimistion to implement – so stright off the bt tht is ecent improvement to the top en. However, tht is pek < href="fctory">power figure, n the < href="https://enginesofwelth.net/ctegory/utomobile/">engine hs clerly lost both < href="fctory">power n torque t other RPM.
Outsie of the enthusist gme, iniviul throttle boies re lmost lwys consiere to be rce < href="fctory">cr prts, n this result is goo exmple of why. Rce crs re riven in the nrrow bn of their rev rnge tht mkes the most < href="fctory">power, n rrely, if ever, nee to ip out of tht rnge. Ro crs, on the other hn, shoul be usble over much wier rnge, so the river hs ccess to torque upon request, regrless of wht RPM the < href="https://enginesofwelth.net/ctegory/utomobile/">engine my be cruising t. The < href="https://enginesofwelth.net/ctegory/utomobile/">fctory vrible intke ws exceptionl for tht purpose. Its vrible geometry (which switche from smll to lrge volume t 4,800rpm) netly explins the new hole in torque up to 5,000rpm, most pronounce roun 4,000rpm. The other ip t 6,800rpm is unusul n will require further investigtion when we o some testing with the finl intke hrwre incluing trumpets of vrying lengths n irbox li n optimising the VTEC enggement point.
So where oes tht put us reltive to our ‘Stge ′ trget of nice roun 300 crnk hp? Some quick mths…
< href="https://enginesofwelth.net/ctegory/utomobile/">fctory mnifol = 9.6rwkW + 7.3kW (mesure rivetrin loss) = 8.9kW/93.5 crnk hp
Multi-throttles = 0rwkW + 7.3kW = 8.3kW/306. crnk hp
…I’m stisfie to cll tht mission success for ‘Stge ′, which ws originlly benchmrke ginst the 987. Cymn S on simplistic < href="fctory">power-to-weight bsis. We’ve even snuck pst the 00hp-per-litre threshol, which is gret for n NA < href="https://enginesofwelth.net/ctegory/utomobile/">engine. However, it’s efinitely not job one with some < href="fctory">power n torque to be recovere t lower RPM, n perhps even more to come from the top en with the right supporting moifictions. I’m estimting weight reuction to be roun kg (4lbs), but currently without the exct mesurements to confirm.
However the primry win is not mesure in tq/hp, but in smiles. Of course, it souns mzing. An intoxicting cresceno tht buils to the VTEC crossover, then bsolutely screms to reline. Don’t believe me?
[embe]https://www.youtube.com/wtch?v=TphSASE86yg[/embe]
Wht my prticulrly impress with those of you who hve gone own the ITB pth lrey is tht the en result is n NSX with completely uncompromise ro mnners. At sensible RPM it genuinely rives like stock < href="fctory">cr. It strts first bng of the key regrless of the wether. The ile is set t 900rpm! We cn chse own the < href="fctory">power n torque but right now hving < href="fctory">cr tht is genuinely rivble with rive-by-wire, vee-configurtion ITB setup is something I’m increibly prou of.
A mssive thnk you to Ash from < rel="nofollow" href="https://www.909motorsport.com.u/" trget="blnk">909 Motorsport n Eric from Apex Composites for the effort, skills n motivtion they provie throughout this project. Without these guys, I my hve by some mircle mnge to get ITB system instlle on the < href="fctory">cr but I never woul hve something tht is so robust, beutifully finishe n relible s wht we hve. Also specil thnks to Rm from RHD engineering, for nswering six million questions n getting me the extr bits I neee to get the project cross the line. A shoutout lso to Tim McLen of < rel="nofollow" href="https://www.instgrm.com/tmcevelopments/" trget="blnk">TMC Developments for the eucte input uring the esign process.
Blke Jones
Instgrm: < rel="nofollow" href="https://instgrm.com/blketjones/" trget="blnk">blketjones
blke@speehunters.com
The SH Grge on Speehunters
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