Nissan CA18DET mootori sisekomponentide muudatused talumaks võimsust 350 kW

Lõputöö teema on „Nissan CA18DET mootori sisekomponentide muudatused talumaks võimsust 350 kW“. Teema eesmärk oli saavutada Nissan 200SX puhul 350 kW-ni suurendatud mootori väliskarakteristikute juures töökindlus vähemalt kaheks hooajaks osalemisel kiirendusvõistlustel Street B klassis ning lõppkiirusvõistlustel. Esmalt oli vaja välja selgitada, millised jõud mõjuvad mootoris ning kuidas nende muutus muudab mootori töökindlust. Sellest selgus, et suurimat tähelepanu väärivad väntmehhanism, õlitus- ja jahutussüsteemid, mootoriplokk ning plokikaas. Suurenenud koormuse juures peab tähelepanu pöörama ka detailidele nagu tihendid ning kinnitusvahendid. Analüüsides erinevaid materjale ja valmistusviise selgus, et väntmehhanismi töökindluse parandamiseks tuleb kepsud ning kolvid vahetada tugevamast ja sitkemast materjalist ning täiustatud konstruktsiooniga sepistatud detailide vastu. Väntvõll peab olema sepistatud ja soovituslik oleks kasutada kõrge pöörlemissagedusega mootoril ka kahekordsete vastukaaludega väntvõlli selle täiuslikuma tasakaalustatuse tõttu. Mootoriploki ettevalmistuseks tuleb see vajadusel puurida ja hoonida sobivasse mõõtu, lihvida kontaktpind saavutamaks pinnakaredus Ra 1,32 ning modifitseerida plokki et paranda karterigaaside liikumisvõimet. Samuti tuleb plokikaane kontaktpinnale tagada tasapinnalisus ning sobiv pinnakaredus. Mootoriploki ja kaane liitmisel peab kasutama suurema tõmbetugevusega tikkpolte, mis tagavad pingutusjõu ka mitmekordsel kasutamisel. Õlitussüsteemi muudatused tagavad kvaliteetse õlikiilu olemasolu ka suurendatud pöörlemissagedusel ja koormusel. Jahutussüsteemi täiustuste eesmärk on tagada suurendatud võimsusega kaasneva suurema soojushulga efektiivne hajutamine ning mootori jahutuse tagamine ka 120 0C temperatuuri juures. Mootori sisekomponentide muudatused prognoositava võimsuse juures töökindluse tagamiseks lähevad 04.05.2014 hindade seisuga maksma 6207,5 eurot.

The objective of this thesis is to construct an engine that would endure two seasons of drag racing and top speed events while producing power in the amount of 350 kW. In addition the car is being driven on the street. The selection of this particular subject is due to the fact that Nissan 200SX – the car on what the CA18DET is most commonly found – is getting increasingly popular amidst young drivers and more so in different types of motorsport – be it drag racing, drifting or track events. Because the power rating of drag racing cars in EDRA Street B Class often exceeds 300 kW, the power on the discussed car is increased to 350 kW. Although the CA18DET is known for having reliability issues, especially when comparing it to the newer SR20DET engine, these problems are mostly due to the age of an average CA18DET – over 20 years. Beacuse the 200SX is a relatively inexpensive car, it is often bought by people with not enough funds to properly service the car. Due to the fact that proper service is the key to an engines longetivity, it is not seldom that a CA18DET breaks down. To make the CA18DET capable of coping with nearly three times the amount of power it came from the factory, the engine must be thoroughly analyzed and some parts of it replaced or reconstructed. To achieve the objective of this thesis, it has to consist of three steps. First it has to be explained, what kind of forces and in how big a scale influence the engines basic components when power has risen from 124 kW to 350 kW and what kind of other changes might be present in the engines operation. Secondly, what kind of problems to the engines longetivity could arise from the power increase. Then a solution to those problems has to be found and explained thoroughly. Last step is to calculate the cost of such modifications. Summarized, the pistons, connecting rods and engine block needed the most attention. Also some changes had to be made to the lubrication and cooling systems and the cylinder head. Due to the forced nature of the engine attention had to be given even to the fasteners and seals. The original pistons and connecting rods are replaced with forged items which are specially designed for racing purposes being stronger and tougher than those produced by the original manufacturer. Because the CA18DET original crankshaft is forged from steel, there is no need to replace it. Modifications to the block include boring, honing and decking. Decking is necessary to achieve a maximum roughness of Ra 1,32. This is necessary to achieve a good seal when using a multi layer steel gasket. The same kind of roughness is needed from the cylinder head. To ensure sufficient and accurate clamping force on the head gasket, studs have to be used instead of head bolts. Changes to the lubrication system are made to ensure a good oil film between the shaft and bearings. Cooling system modifications include the installation of a more efficient radiator and an increase in the cooling system pressure. This is necessary to raise the coolant boiling temperature to 120 0C. Total cost of all modifications is 6207,5 euros.