big28 and stock injectors, computer and maf

[john891]

My t25 took a crap. I was considering having it rebuilt or buying another but at the same time I would like to upgrade.

My question is could I slap a Big28 on it and run low boost levels on stock injectors, maf and computer? If I did would It still run and drive the same as a stock turbo? I was thinking it would if it is theroretically pushing the same amount of air as the stock turbo it would run the same.

thanks

[NZO]

Big28 is not the same as a stock t25 turbo so no it will not feel the same. If you want something around 350whp level I would investigate other turbo options; gt2871r for example. Sure they cost a little more but the price is worth the difference, and this is comming from a big28 owner. Alternatively if you are satisfied with a lower power level (and higher boost levels) and are on a budget big28 isnt a bad choice.

[wootwoot]

It is not theoretically pushing the same amount of air though. It is pushing more air at the same psi, to a degree atleast. This works better when you are actually in the efficency range of the turbo. If you put that turbo on, I would personally do anything I could to make it not go over say 7psi until you could afford the bigger maf/injectors/tuning. Dont want to go blowing your engine now

[NZO]

True it is flowing more air but luckily the stock injectors can handle it. I have big28 z32 maf and stock injectors with no boost control (stock actuator control). I have seen an inj duty cycle of 99.9% on my PFC before but thats only one or two times during a drift event and probably due to boost spiking with fast throttle inputs. During normal driving though it never goes over ~80% no matter what I do. On cold nights (60F) it will spike to ~8.2psi at the very most, never seen it go over that.

[john891]

interesting, thanks.

I think I might just get my t25 rebuilt because I have other things that need the money. You guys have any recomendations on where to send it for a rebuild?

[KOUKI KA-T]

Here, see the AFR's for yourself. We just dyno'd this s13 redtop 2 weeks ago with the big28 upgrade, stock MAFS and injectors and timing. No fuel managemnt and 13psi....
http://img.photobucket.com/albums/v378/srhamlin/F1dynomeet014.jpghttp://img.photobucket.com/albums/v378/srhamlin/F1dynomeetgraphChris.jpg

[NZO]

Interesting to see such high boost with the big28 and stock injectors. I recall someone else running 14 and saying it wasnt maxing out the injectors. Do you have any idea what kind of duty cycles the car was seeing there KOUKI KA-T?

[wootwoot]

I was under the impression that the MAF was maxed out far before that, the injectors as well...

[Silverbullet]

correct me if i'm wrong, but dosn't the oem MAFS and 370cc injectors limit the power to 240-250whp no matter what turbo it has?

[KOUKI KA-T]

I've seen several 240's make 275-300 on the 370's, but yes they are pretty much maxing out both injectors and mafs. I supect the mafs was maxed and that it's the reason it starts to lean out up high. I think the original poster would be fine upgrading to the big28 on stock boost.
I'm not recommending that anyone go plop in a big28 on their SR and crank the boost at all, it was just for referance. Every car is different, the same day we dyno'd a stock redtop with only bolt ons and 11psi that was hitting mid 14 AFR's.

[john891]

So i guess the big28 would be fine to run about 8-9psi until i got a tuned ecu injectors and maf

[KOUKI KA-T]

So i guess the big28 would be fine to run about 8-9psi until i got a tuned ecu injectors and maf

IMO yes, but I'd still suggest spending $50-$65 to take it over to a dyno and do a couple pulls w/ wideband to make sure it's not running too lean. Again I've seen a few stock SR's that run extremely lean in stock form, not sure why this is.