Big 16g on a stock car

[NanaVr4]

My 1991 GVR4 has a bad oil leak from the turbo. I want to replace it but the stock 14b is tough to find. I’ve found more 16g turbos and I’ve read that it is a direct bolt on but I’m not sure if I could run it without an upgraded fuel pump/enjectors/ecu.

Could I run a 16g on a stock GVR4 or are all the previously mentioned parts necessary?

 

[Dialcaliper]

Small, big and maybe even an evo3 16g will run just fine, with some caveats.

Without upping the boost, you’ll basically be getting stock power with some slight extra lag, especially if you still have the small stock intercooler. You’ll need a manual boost controller to turn up the wick. But you’ll also be limited by the stock injectors and fuel cut to somewhere around 13-15psi depending on whether you are comfortable pushing the injectors past 80% duty cycle.

If all you plan to do is swap in a small 16g, and not touch anything else including stock boost, yeah, you’ll be just fine.

 

[gvr4ever]

2nd. You might have a micro amount more turbo lag, but you will be more future proof. Completely safe to do.
Exhaust and IC without even touching the boost will give you a faster turbo spool. You only need larger injectors, fuel pump, AFPR, and tune for higher boost (stock MAF sucks for more boost). Way back in the day, with a fuel pump rewire, I ran 14psi of boost (93 pump) . On cold days, the stock MAF would hit the wall and I'd get fuel cut.

 

[Dialcaliper]

2nd. You might have a micro amount more turbo lag, but you will be more future proof. Completely safe to do.
Exhaust and IC without even touching the boost will give you a faster turbo spool. You only need larger injectors, fuel pump, AFPR, and tune for higher boost (stock MAF sucks for more boost). Way back in the day, with a fuel pump rewire, I ran 14psi of boost (93 pump) . On cold days, the stock MAF would hit the wall and I'd get fuel cut.

If it’s more of a daily driver, you settle for an Evo 8 (190lph) fuel pump and aren’t planning anything “big”, you can even skip the AFPR and you’ll still be able to max out a small/big 16g with just some Evo 560cc injectors, tune and exhaust/intercooler - cheap and still fairly reliable 300-350hp+ on pumpgas

 

[NanaVr4]

If it’s more of a daily driver, you settle for an Evo 8 (190lph) fuel pump and aren’t planning anything “big”, you can even skip the AFPR and you’ll still be able to max out a small/big 16g with just some Evo 560cc injectors, tune and exhaust/intercooler - cheap and still fairly reliable 300-350hp+ on pumpgas

It is a daily. I probably should have mentioned I have a JDM VR4 so it has stock 510cc injectors. The fuel pump just went out so I ordered a walbro 255HP pump, I was told by a friend that a fuel pump upgrade would be fine on its own but I saw a forum post that a bigger fuel pump could flood the stock FPR. Should I invest in a AFPR and if so do you have any recommendations?

Thank you all for the help.

 

[Turbo99]

It is a daily. I probably should have mentioned I have a JDM VR4 so it has stock 510cc injectors. The fuel pump just went out so I ordered a walbro 255HP pump, I was told by a friend that a fuel pump upgrade would be fine on its own but I saw a forum post that a bigger fuel pump could flood the stock FPR. Should I invest in a AFPR and if so do you have any recommendations?

Thank you all for the help.

Probably not a bad idea. FPR kits for these cars are relatively inexpensive and easily installed. That being said, I ran a Walbro 255 on my 2g back in the day on the stock regulator and did not have any issues personally.

 

[Dialcaliper]

It is a daily. I probably should have mentioned I have a JDM VR4 so it has stock 510cc injectors. The fuel pump just went out so I ordered a walbro 255HP pump, I was told by a friend that a fuel pump upgrade would be fine on its own but I saw a forum post that a bigger fuel pump could flood the stock FPR. Should I invest in a AFPR and if so do you have any recommendations?

Thank you all for the help.

Are you sure you have the yellow-top 510cc? Those only came on the evolution/RS models that were already equipped with a big 16g turbo from the factory. Standard 450cc are blue-top which came on all other JDM and USDM cars as well as the 1G DSMs

If you do have yellow top injectors, those will get you reasonably far, but if you actually have those, your stock turbo would be a big 16g, not a 14b

You might get away with a 255 pump as long as you don’t rewire it. FPR overrun tends to happen at idle/low load whenever fuel is being forced through the FPR return rather than going through the injectors into the engine

 

[NanaVr4]

Are you sure you have the yellow-top 510cc? Those only came on the evolution/RS models that were already equipped with a big 16g turbo from the factory. Standard 450cc are blue-top which came on all other JDM and USDM cars as well as the 1G DSMs

If you do have yellow top injectors, those will get you reasonably far, but if you actually have those, your stock turbo would be a big 16g, not a 14b

You might get away with a 255 pump as long as you don’t rewire it. FPR overrun tends to happen at idle/low load whenever fuel is being forced through the FPR return rather than going through the injectors into the engine

The injectors in there are definitely yellow top but they could have been aftermarket for all I know. The previous owner didn’t give me much info on the car.

 

[Dialcaliper]

The injectors in there are definitely yellow top but they could have been aftermarket for all I know. The previous owner didn’t give me much info on the car.

Here’s an interesting old post with some scanned JDM chassis code breakdowns

JDM Parts Catalog: Model Specs, Option Codes, Vin Boundaries

Did some scanning today. I will not be scanning the whole document (its 950 pages) Caps& ASA cover all the part numbers. However this I the first section of the book and covers Model Breakdown, Options and Vins applicable for all production variants and all years. A2 Is the year change...

www.galantvr4.org

E39A with SNPF is the regular VR-4
E38A/E39A with SNPF4 is the VR-4 RS which definitely had the yellow top and big 16g

Anything else with yellow top/B16g from the factory would have had a badge (Evolution, Monte Carlo), and might also be coded as an RS. All would have a B16g from the factory. Dumb question, but have you verified that your “stock turbo” is in fact a 14b and not a big 16g?

 

[GSTwithPSI]

I want to replace it but the stock 14b is tough to find

Just rebuild it. It's a couple hour job including R&R and way cheaper.

This is 1 example of many kits you can find on the web:

MHI 14B 16g 20g Turbo Rebuild Kit - Turbo Lab

Buy MHI 14B 16g 20g Turbo Rebuild Kit Here. We offer Upgraded Genuine 16g Turbo Rebuild Kits, which also fit FP Red, Green, Black, & MAP EVO X turbos!

turbolabofamerica.com

 

[gvr4ever]

Are you sure you have the yellow-top 510cc? Those only came on the evolution/RS models that were already equipped with a big 16g turbo from the factory. Standard 450cc are blue-top which came on all other JDM and USDM cars as well as the 1G DSMs

If you do have yellow top injectors, those will get you reasonably far, but if you actually have those, your stock turbo would be a big 16g, not a 14b

You might get away with a 255 pump as long as you don’t rewire it. FPR overrun tends to happen at idle/low load whenever fuel is being forced through the FPR return rather than going through the injectors into the engine

255 pump will over flow the stock FPR for sure. I tried that, and it ran pig rich. I ordered a AFPR right away. The 2G DSMs could run a 190 without a AFPR, but I thought 1Gs were more sensitive to higher fuel pressures. I haven't tried it myself on a Galant VR4, so maybe it will be ok.

 

[Dialcaliper]

255 pump will over flow the stock FPR for sure. I tried that, and it ran pig rich. I ordered a AFPR right away. The 2G DSMs could run a 190 without a AFPR, but I thought 1Gs were more sensitive to higher fuel pressures. I haven't tried it myself on a Galant VR4, so maybe it will be ok.

There’s also the option of wiring in a fuel pump resistor and relays like the one the Evo uses - basically a power resistor to drop the pump voltage off-boost to prevent overrun, and a relay to bypass it wired off something like a Hobbs pressure switch.

 

[gvr4ever]

There’s also the option of wiring in a fuel pump resistor and relays like the one the Evo uses - basically a power resistor to drop the pump voltage off-boost to prevent overrun, and a relay to bypass it wired off something like a Hobbs pressure switch.

The 255 over ran the stock FPR, I don't think the air fuel ratio was correct till around 3psi before the 1:1 boost / fuel pressure was correct. I should have only gotten a 190. If I ever have to replace my fuel pump, I'll only get the 190.