Engine Out, Improving Response

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Posts: 3
Joined: Mon Feb 20, 2017 6:02 pm
Car: Silvia S15

Engine Out, Improving Response

Postby lsmith » Sun Sep 17, 2017 6:11 pm

Replaced my rattley VCT with camgears... and discovered that it had been masking a somewhat more serious rattle... spun bottom end bearing possibly caused by oil starvation. So engine is out and fully disassembled, from first inspection doesn't look terminal... crank can probably be reground. A wise man told me to look at this as an oppurtunity... so I'm looking to do some upgrades.

This is my daily driver, so I want reliable usable power on the street... aim is 300kw on E85 with maximum response. I feel the 3071 is too laggy in the current setup / goals.

Current Build: GTX3071 T25 IWG (low mount, single scroll, 0.64 A/R), Plazmaman plenum, FMIC, TOG ex. manifold, 3" Exhaust, Wisco Pistons, Manley Rods, Solid Lifter Conversion, Tomei 260/260 cams, Bosch 1650cc EV14, Haltech Platinum Pro, etc

a) Stroker Kit - Use 91mm stroke to improve low rpm tq and bring current turbo on boost earlier
b) Change Turbo - Move to high mount with twinscroll EFR turbo (probably 6758)
c) VET Head - Convert to SR20VE VVL head
d) Others - Port and Polish, Valve Job, Crank Balancing, etc

Anyway just want to get an opinion on what will give me the best bang for the buck / least hassle. I've got access to a decent workshop, so I can do most labour / assembly on my own.

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'96 S14 Coupe: SR20VET
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Location: DFW, Texas

Re: Engine Out, Improving Response

Postby 2_Liter_Turbo » Sat Oct 28, 2017 10:42 pm

What's too laggy for you? What RPM are you hitting full boost? I had a twin scroll GT3071R and I had full boost/TQ right around 4k RPM. If you want to save money, a GTX3067 would be a good match (go twin scroll for slightly better response). I personally am in the middle of upgrading to an EFR myself (7163), but I don't have any seat time in it yet to give an idea. A stroker will make boost quicker, but it may be overkill for a street car. I think a turbo change would be best. In my opinion, VE heads are better suited for cars that spend most of their time at the track for the cost involved in the conversion. I still have a DET head, and never had any issues. If you're doing an engine build, but want to keep cost in check, I would keep your head the way it is, throw good parts at the bottom end with a quality shop doing the machine work, and possible swap out your turbo to match your application. The 260 cams are good, that's actually what I've ran for years. If your crank is toast and you can't find a clean one for a decent price, then maybe a stroker setup would be in the cards.

Posts: 3
Joined: Mon Feb 20, 2017 6:02 pm
Car: Silvia S15

Re: Engine Out, Improving Response

Postby lsmith » Sat May 19, 2018 7:23 pm

Woops, bit late on the response.

Yeah got away lucky in the end, just reground the crank, added some new bearings and reassembled... Seems to be running OK so far (fingers crossed).

Just recently bought (but haven't installed yet) a complete Twinscroll EFR7163 + Fullrace setup off a nutty sr20vet... makes 390 rwkw, didn't believe him at first until he showed me:

Anyway I opted for this turbo over the 6758 because in the long run I'll probably go a VET head.

Based on a full load 98RON run in 3rd gear (on the street) my GTX3071 setup is making:

RPM = Boost
3.0K = 1.5psi
3.5K = 4psi
4.0K = 10 psi
4.5K = 21 psi

In 2nd gear this is shifted up 500 RPM or so. It only really starts to pull between 4-4.5K in 3rd and 4.5-5K in 2nd. Except for drags, I feel this is a pretty useless powerband on the street... would prefer something in the 3.5-4K range. There may be some gains I could make with the ignition timing, we road tune our cars with a knock detector so we're mostly just guessing the optimal timing where its not knock limited (low rpm, light loads, etc).

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