Billet 7875 Results thread
TECH Junkie
Joined: Jul 2015
Posts: 3,012
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Joined: Aug 2007
Posts: 24,241
Likes: 89
From: Turnin' Wrenches Infractions: 005
TurboSmart WG and XS Speed BOV. Both work good.
I bought a Huron Speed 7875 that I am going to install once i get the engine back together and was also wondering if anyone else had results for the Billet 7875s.
Last edited by SLWRDE; Jan 13, 2018 at 10:34 PM.
i went 10.99 & 133spinning on 19psi 3800lb truck, 4.8 with a 224/228 mid .5xx lift cam, 4l80e and a 10.5 afr, pump 92. there is a lot more left in it obviously, but traction and power control issues kept me from leaving harder than a 2.xx sixty
hopefully next year I can get the sixty down to a respectable 1.60' and run half track passes since I dont have a bar/cage/etc..
hopefully next year I can get the sixty down to a respectable 1.60' and run half track passes since I dont have a bar/cage/etc..
Joined: Aug 2007
Posts: 24,241
Likes: 89
From: Turnin' Wrenches Infractions: 005
Im confident the two cars i built in the last 6 months will perform well with the 78/75s. They light off quick and make boatloads of torque on the 5.3 engines.
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these are a good turbo but the 75 mm turbine and .96 housing are still a bit restrictive on a 5.3 at higher rpm. so to much cam will not help the top end just make it soggy down low.
we did a test on my buddys backhalf Camaro . with a 2005 5.3 with triple 12 cam , 400th, 3.73 gear and 31.5 by 12 slick leaving at 12 psi and running 20.5 psi max it ran
9.40 at 141 mph with a cast on3 78/75.
swapped to a borg 80mm with 83 mm turbine 76mm exducer and t4 1.25 housing it ran 9.31 at 142 mph all else being the same. spool was much slower due to borg being bigger heavier parts. but iat did drop about 25 degrees.
I'm sure turning them up more we whould have seen a bigger difference but for the money a 78/75 is a good turbo.
I'm not sure the bilit helps much as they already spool fast and I think the turbine wheel and housing are the limiting factors.
we did a test on my buddys backhalf Camaro . with a 2005 5.3 with triple 12 cam , 400th, 3.73 gear and 31.5 by 12 slick leaving at 12 psi and running 20.5 psi max it ran
9.40 at 141 mph with a cast on3 78/75.
swapped to a borg 80mm with 83 mm turbine 76mm exducer and t4 1.25 housing it ran 9.31 at 142 mph all else being the same. spool was much slower due to borg being bigger heavier parts. but iat did drop about 25 degrees.
I'm sure turning them up more we whould have seen a bigger difference but for the money a 78/75 is a good turbo.
I'm not sure the bilit helps much as they already spool fast and I think the turbine wheel and housing are the limiting factors.
Freeky,
When I called BTR awhile back and told them my setup/goals which is a 5.3 and a HSP 78/75 with a goal of 600-700hp they said the Stage 1 222/227 .602"/.598" 113+3 would work the best. I would imagine with that BTR Stage 3 cam 230/235 .609"/.610" 114+4 it would depend on your setup and how much power you want.
When I called BTR awhile back and told them my setup/goals which is a 5.3 and a HSP 78/75 with a goal of 600-700hp they said the Stage 1 222/227 .602"/.598" 113+3 would work the best. I would imagine with that BTR Stage 3 cam 230/235 .609"/.610" 114+4 it would depend on your setup and how much power you want.
Well I talked to Jarret (Stock48) last night for almost an hour about my setup (5.3, HSP 7875 in a 1965 Cutlass) and what cam he thinks I should use. Wow, what a great guy who is a wealth of knowledge. So we decided on a 218/222 .585 112 LSA. Man I can't wait to get this thing installed. Thanks everyone who recommended him. I will post results once I get everything back together.
Take it for what its worth, but I have designed a handful of cam lobes as a mechanical engineer and spec cams regularly for customers. For a 243 headed forged 5.3 (~9.5:1 CR) with a turbonetics BB 7875 cast turbo, I ran a lot of numbers as I always do, and what I landed on was 219/226.5 @ 0.050 with 115 LSA and placed my ICL at 110. My lift is right around 0.600 +/- 0.005 for each lobe.
The result is an earlier exhaust valve opening (54.5 BBDC) to start the blow down process sooner due to high back pressure from the 75mm 0.96 turbine assembly. This helps reduce pumping losses through the exhaust side and starts spooling the turbo sooner. Additionally, this results in -6 degrees overlap which is needed with high exhaust back pressure setups. And my intake valve close occurs at 38.5 ABDC which gives a nice dynamic CR and good bottom end torque and turbo spool.
Hope that helps someone
-John
Roastin Performance
The result is an earlier exhaust valve opening (54.5 BBDC) to start the blow down process sooner due to high back pressure from the 75mm 0.96 turbine assembly. This helps reduce pumping losses through the exhaust side and starts spooling the turbo sooner. Additionally, this results in -6 degrees overlap which is needed with high exhaust back pressure setups. And my intake valve close occurs at 38.5 ABDC which gives a nice dynamic CR and good bottom end torque and turbo spool.
Hope that helps someone
-John
Roastin Performance
haha thats some cognitive resonance for me.
i took every cam i could find recommended for the 7875 and plugged it into the cam motion cam timer. very little variation on that theme of -6* overlap. most were within a degree or two.
i took every cam i could find recommended for the 7875 and plugged it into the cam motion cam timer. very little variation on that theme of -6* overlap. most were within a degree or two.
