NZ Performance Car - - Super Score -

The hum­ble SR four-banger is per­haps one of the most pop­u­lar en­gine swaps world­wide, with it seen adorn­ing more en­gine bays than we have room to list here. Favoured for its bang-for-buck per­for­mance and re­li­a­bil­ity, non-turbo (DE) and turbo (DET) can be had for chump change, and the boosted ex­am­ple has been proven to be eas­ily squeezed to 250kW with sim­ple up­grades. But, when it comes to Mazda chas­sis, SR swaps are still rel­a­tively un­charted wa­ters. Alex Browne from Christchurch saw on­line that peo­ple were us­ing the RX-8 gear­boxes be­hind SR20s as up­grades from the fac­tory units, and thought to him­self, why not just put the SR20 into an RX-8? And that’s what he did.

The SR isn’t huge di­men­sion­ally — mea­sur­ing in an al­most square 630mm long, 600mm wide (with hot and cold sides), and 600mm tall — mak­ing for a semi-has­sle-free in­stal­la­tion into the RX-8’s deep and long en­gine bay. To achieve a level fit at the height that he de­sired, Alex opted to re­lo­cate the al­ter­na­tor to the op­po­site side of the block; how­ever, due to the front-sumped con­fig­u­ra­tion, the cross mem­ber had to be mod­i­fied heav­ily for clear­ance. “I’ve done a few en­gine swaps now, and it was noth­ing too dif­fer­ent from the oth­ers. All I had to do was re­make the cross mem­ber, which I’ve used 60mm tube to con­nect what was left of the orig­i­nal unit af­ter cut­ting room for the sump to sit,” says Alex.

What was left of the orig­i­nal cross mem­ber formed the ba­sis of the new en­gine mounts, a cus­tom perch made from 6mm steel plate that would ac­cept the fac­tory SR mounts. The steer­ing rack’s mount­ing points were also moved for­ward with the tube sec­tion to al­low room for the pul­leys.

And, like the gear­box swaps that he had ini­tially seen on the in­ter­net, the fac­tory RX-8 driv­e­train has been re­tained, with an SR bell­hous­ing and a thrust-bear­ing spacer to mate the five-speed to the back of the mo­tor. This meant that noth­ing had to be chopped or fab­ri­cated out­side of the en­gine bay.

Over­all, Alex tells us that he rates the con­ver­sion a good seven out of 10, com­ment­ing: “The steer­ing is a lit­tle twitch­ing, and the mo­tor is a bit higher than the Re­n­e­sis, but it makes good us­able power, is a rel­a­tively straight-for­ward con­ver­sion, and is a tad more re­li­able.”

SR20DET ORI­GIN CHAS­SIS: Nis­san Sil­via (S15) CA­PAC­ITY: 1998cc CON­FIG­U­RA­TION: Straight-four turbo BORE/STROKE: 86mm x 86mm COM­PRES­SION: 8.5:1 FAC­TORY POWER: 151kW / 275Nm WEIGHT: 149kg NOTES: T-25G turbo,

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