Which one to choose between S13 redtop/blacktop (flat head) SR20det and S14/S15 (hump head, with intake NVCS) SR20det

(This is answers to questions asked by mapler520)


TOPIC: Which one to choose between S13 redtop/blacktop (flat head) SR20det and S14/S15 (hump head, with intake NVCS) SR20det

The question:

Actually i am looking to change either sr20det or 1jz,but 1jz is lack of performance parts and the parts are getting rare and expensive,and then i look into sr20det and found that the response of sr20det is amazing,so bro if i am looking for sr20det halfcut,should i look for s13 blacktop or s14 blacktop?some people say that if going to mod the engine better take s13 sr20det,if for normal driving take s14 halfcut with vct system,they say its a bit hassle about the vct system,is that true?i think if i get sr20det i have to upgrade it to at least 300rwhp to push my a31,stock sr20det i dont think able to push my a31


The Answer:

It doesn't really matter actually if you choose between any of the models. They do make some difference when in stock mode. But when u upgrade to 300rwhp and above, things started to be different in common ways i.e.:

in stock form:
-SR20det redtop/blacktop S13 (flat head): no intake NVCS (nissan variable valve system), better cyl head intake/exh port design.

Engine designer calls the intake port design as High Entry or Fast Draft...becaust the intake port inlet sits high on the side of the cyl head and very min bend on the runner design. Therefore air/fuel mix can flow much faster into the combustion chamber with less restriction. T25 turbo. other than this everything basically are quite the same i.e. oil pump, cam spec and internals.

-SR20det blacktop S14 (hump head): with intake NVCS, new cyl head intake/exh port design (due to stricter emission regulation, nissan designers design it this way, it highly reduces NOx emission but cause slower intake air speed through the cyl head port and runner).

As opposed to the high flowing redtop cyl head, for s14 SR, the intake entry port sits low on the side of the cyl head. forcing the design of the runner to have tighter bend than redtop SR design. so flow is reduced to higher restriction of the bend. Turbo is T28 single ball bearing if i'm not mistaken..Other than this difference and NVCS, other things are quite the same with redtop SR.

in upgraded form:

letsay stage 1 (i mean like <310rwhp). common mods like GTR fuel pump, 550cc inj, fuel regulator, power FC/safc/haltech,maintain stock turbo or upgrade to a bit bigger like s15 dual ball bearing turbo, GT2530r (hks gtss), GT2871r (hks gtrs), boosting at 1 to 1.3bar, stage1 cams like HKS step 1 or tomei poncam (can maintain using intake NVCS for s14 SR engien), boost controller, FMIC, alum rad and etc.

or..stage 2 (like >310rwhp), all the common supporting mods, higher cc inj like 850 to 1000cc inj, standalone ECUs, ful engine rebuild+balancing, forged pistons n rods, all the arp studs, larger capacity turbo like GT3071r (hks 2835), GT3076r or GT30r (hks 3037), GT35 and so on...boosting > 1.3 bar (1.3 to 1.7 or even 1.9bar for some super monster dudes hehe)...stage 2 and above cams like Tomei procam/BC stage 2/hks step 2...cyl head full port n polish and etc.

so u see, when u go for stage 2 upgrades...normally engine builders/tuners will remove intake NVCS for s14 SR and use adj cam sprocket (making it the same like redtop/blacktop flat head SR. and then performance difference between the above mentioned cyl head design difference..i think hardly noticeable..maybe redtop/blacktop flat head SR can perform around 10 to 30% better than the more conservative s14/s15 cyl head.

therefore...u can choose which ever engine model that u want. or i can offer some advice for the selection:

1. if u want to maintain stock: u can choose the newer S14 or s15 SR because it got intake NVCS, and important fact that the engine is newer. i always remember advice from my friend kenji (nickname mist in DCM)...an engine health or to gage the life status of the engine is based on the mileage...low mileage means that he engine is young :) and high probability that the engine is healthy in everyway (mechanically, electrical...wiring n etc) all in good condition.

2. if u want to upgrade to stage 1: u can choose either flathead or s14/s15 SR

3. if u want to upgrade to stage 2 later and a full engine rebuild + full cyl head port n polish..i would personally choose a flat head SR :)..the reason being is..i want to get the most out of the cyl head performance if u know what i mean.

regards,
Jai Bluebird