Taking a Stock Engine with Stock Turbo to the limit....

[84BuickGNYorkPA]

Awesome!

 

[V6sleeper]

Fantastic

 

[Street Lethal]

Looking like your headed for the record pretty quick

Well, if we add that six hundred pound difference to it, it comes out to about a 12.20 ET lol...

I'm only kidding lol, great job Murph...

 

[turbo89]

Well, if we add that six hundred pound difference to it, it comes out to about a 12.20 ET lol...

I'm only kidding lol, great job Murph...

I think about things like this all the time .. just how much easier it is on the car when it weighs less... think about how much easier life a 200r4 would have if Turbo Buicks only weighed 3000#'s

just makes you realize just how heavy these cars are ...

Great job Murph ! NOW put a 75 hp hit on it

 

[murphster]

Thanks for the comments guys. Went faster than I thought it would right off the bat. I figured low 12s or maybe high 11s to start off with until I got it figured out. I had to guess what to launch at and also didn't want to burn a run leaving too hard, but I'll definitely have to leave harder to get the 60fts down.

I have a lot of data to look over and will post up some more details as I go through them....

 

[murphster]

First thing is the converter and how it worked out. I left the same th400 trans and 9.5" nl PTC converter in from the old 9 sec engine setup. Figured it would tighten up and it did feel good on the street.

I had to use the data from the first run since the mph was off on the second run a little. I crossed the line at 115.4 mph and 4700. I'm on 28" drag radials that have minimal growth and 3.23 gears. Using a couple different calculators I came up with 6.7% and 5.5% slippage. Also, my rpms dropped down to 4300 on the shifts.

So thats great slippage for a 9.5" nl that wasn't bought for this purpose. And using the 3.23s that were already in my car we thought was going to work out well to keep the rpms down.

So how to relate this to other typical stock setups that have worked well? First, I'd say that my coupling rpm may be a little high. A stock restalled D5 may drop to the bottom 4000s on a shift. So I could be leaving some on the table there if I'm above peak torque. Second, I'd say a locked D5 running on 26" tires or even 27" is a good stock setup. A locked D5 with 0% slippage on 26" tires would need around 4860rpm to run 110mph, a typical good stock engine pass. 115.4mph would have needed 5090rpm. 26" slicks that grow to 27" or 27" drag radials would need 4680 @110 and 4900@115.

So to put in perspective, I'm only turning the same rpm at 115mph on my 9.5" nl converter that a typical stock setup would do with a lockup converter on 27" tires at 110mph.

Ideally, I should switch to a tighter 9.5" converter as I'm leaving some performance on the table. But I can still go almost 120mph at 4900rpm even if my slippage goes up to 8% so I should be ok.

 

[Mr.Spool]

Well, if we add that six hundred pound difference to it, it comes out to about a 12.20 ET lol...

I'm only kidding lol, great job Murph...

The whole physics things really changes everything

 

[murphster]

Yeah, I'll try to keep it simpler though with the rest of the data lol. Main thing is trying to find the sweet spot for the stock engine/turbo combo. From picking people's brains I learned rpm needs to be limited to somewhere in the high 4000s to 5000 before power starts dropping off on stock stuff and figured I'd be in the ballpark with my setup. My rpm only drops to 4300 on the shifts though, which may be on the high side for peak torque on stock engine. If it dropped to say 4100 it may make more torque and give better acceleration, more like a locked stock D5....

Anyway, keeping it on that topic... I have a FAST accelerometer and logged g force on my two runs. Its useful for picking shifts points. Shift too late and the g force will go down and jump up after the shift. Shift too soon and the g force will jump down after the shift. Again, based on other peoples knowledge I was shooting for somewhere in the high 4000s to no more than 5000 rpms to shifts at. I shift manually with my th400.

1st run I shifted at 5000 on the 1-2 and the second run I shifted at 4850 on the 1-2. The accelerometer showed that 5000 was too high on the shift and 4850 was closer but still a little high. I think 4700ish will end up being close to optimal. I could feel the car starting to nosing over at 5000 btw. I never would have guessed to shift that low. I shifted at 4700 on the 2-3 both runs. I was aiming a little higher but logs showed 2-3 shifts looked good.

 

[murphster]

Here is the accelerometer data, green line. You can see on the 4850 shift the jump up is smaller.

Here is a side by side that maybe shows a little better. 5000 on the right, you can see the jump is bigger. 2-3 shift doesn't even register.

 

[seedling]

First thing is the converter and how it worked out. I left the same th400 trans and 9.5" nl PTC converter in from the old 9 sec engine setup. Figured it would tighten up and it did feel good on the street.

I had to use the data from the first run since the mph was off on the second run a little. I crossed the line at 115.4 mph and 4700. I'm on 28" drag radials that have minimal growth and 3.23 gears. Using a couple different calculators I came up with 6.7% and 5.5% slippage. Also, my rpms dropped down to 4300 on the shifts.

So thats great slippage for a 9.5" nl that wasn't bought for this purpose. And using the 3.23s that were already in my car we thought was going to work out well to keep the rpms down.

So how to relate this to other typical stock setups that have worked well? First, I'd say that my coupling rpm may be a little high. A stock restalled D5 may drop to the bottom 4000s on a shift. So I could be leaving some on the table there if I'm above peak torque. Second, I'd say a locked D5 running on 26" tires or even 27" is a good stock setup. A locked D5 with 0% slippage on 26" tires would need around 4860rpm to run 110mph, a typical good stock engine pass. 115.4mph would have needed 5090rpm. 26" slicks that grow to 27" or 27" drag radials would need 4680 @110 and 4900@115.

So to put in perspective, I'm only turning the same rpm at 115mph on my 9.5" nl converter that a typical stock setup would do with a lockup converter on 27" tires at 110mph.

Ideally, I should switch to a tighter 9.5" converter as I'm leaving some performance on the table. But I can still go almost 120mph at 4900rpm even if my slippage goes up to 8% so I should be ok.

Man this is very impressive! Not only from an information perspective, but, the fact that you would take the time to conduct such an experiment! Kudos to you for what is a huge amount of work! Thank You!

And what an illustration this is for anyone (stock or no)! It just goes to show you how many of our cars have some sort of issues holding them back.

Just can't say thanks enough, for taking the time and effort to do this! As it's very helpful for those of us with fewer upgrades! Even down to the tire size as that has been something I've contemplated myself. Again thanks for the write up and sharing the information! Thank You!




Sent from my iPhone using Tapatalk

 

[murphster]

Glad the information is helpful. I know a lot of people don't share a lot but I've always been open. I like having everything written down to refer to also lol as it gets hard to remember the details and what and when it was done. I'm still learning too.

 

[juan89]

Thanks, for sharing.

 

[TurboBob]

for a stock engine, peak torque will likely be the lowest RPM that you can get full boost, its more a question about where it starts to fall off too quickly.

Bob

 

[murphster]

The last thing that ties all this together is backpressure. I'm not an expert on it but I think of it as turbo restriction. A huge turbo will have almost no restriction but will be hard to spool. A very small turbo will have a large restriction but be able to spool very quick. As you turn up the boost on a small turbo the restriction will become an issue. Also, as you run higher rpm the restriction will become an issue too. Easiest way to see whats going on is to measure the backpressure psi in the exhaust pre turbo and compare it to the boost psi the turbo is making, called backpressure ratio. In general, the lower the ratio the more efficient the turbo and 1.5:1 or less is a ballpark good ratio and higher than 2:1 is not efficient although you can still make power.

The stock turbo works best at low rpm because the ratio will get very high at large rpms. It wouldn't be a good match to an engine or cam that shifts the torque curve to a high rpm. A good reason to keep the rpms down.

Same with running high boost.... after somewhere in the low/mid 20s boost the ratio starts to get high and you get diminishing returns. The stock intercooler is a big restriction and you may lose a few psi from the turbo to post intercooler. So while you may see 22psi boost on your gauge, the turbo may be outputting 26psi to get tnat on a stock intercooler. I'm running a large front mount intercooler that I'm guessing has only a 1psi pressure loss. So I may be able to get 25psi boost on my gauge while the stock turbo is still putting out the same 26psi. If I keep making more power as I turn it up we'll know if the less restrictive front mount makes a big difference.

On my old race engine and 71 turbo, I measured a backpressure ratio of just 1.3-1.4 from 20psi to 27psi boost. Turbo wasn't being worked hard. Well, at 20psi boost I am already at a 1.9 ratio on the stock turbo and hit 2.2 at peak rpm before the shifts.

The turbo doesn't like high boost in the high 4000s rpm it seems. The ratio stayed about the same at 1.9 in third gear going from 20psi to 21psi on the second run in the 4600rpm range. However, on the 1-2 shift it peaked at 2.2 at 4850 on the second run and 2.1 at 5000 on the first run. The ratio goes up with rpm. As I up the boost the higher rpms will really start to increase the ratio it looks like. Another reason to keep the shift points low...

The turbo data is showing what the accelerometer data also reflected, keep the rpms low.

 

[murphster]

Backpressure, run 1 vs run 2. Only about 1 more psi boost on the second run but Backpressure goes up about 2 psi since its around a 2:1 ratio to to boost. Definitely increases on the shifts while the manifold boost remained steady (not shown).

 

[Nigel]

Murphster,

Thanks for sharing this information, this takes a lot of time and money to do this. Bison has shared a ton of info like this also. Fantastic contribution to those that want to know what makes a turbo buick tick.

Since the .63 garret housing has been used with larger turbos, the restriction I am guessing is the turbine wheel and the outlet diameter(exducer). In general, centrifugal turbines are a partial reaction design and therefore you get a pressure drop through the wheel. So you get a pressure drop in the radial nozzle of the turbine housing, you get a pressure drop through the reaction of the wheel, and then you have to exit through the diameter of the housing exhaust, which is proabably some amount of additional drop especially on a small exit diameter. So it looks like the wheel or the exit is starting to choke at the higher RPMs and boost levels. Any plans to run other turbos once you have rung out the stock turbo?

 

[murphster]

I don't know... once I find the limit then there are probably a few things to test out to see if it makes any difference. And I'm on pump gas and alky too. Maybe try out E85 or different fuel. I think the turbo will be the limiting factor though.

And if I upgrade the turbo then the engine will probably become the limiting factor. Upgrading the cam and even a minimal port on the heads will probably make a big difference. It would be cool to see how far I can push a stock engine on a bigger turbo though and probably will be the next step down the road, but could be a while....

As far as your statement about the exhaust wheel being the limiting factor, not a turbo expert but that seems to be the case. From what I understand even though the same .63 Garrett Housing is used on other turbos all the turbine wheels are larger than the stock one. So even when you upgrade to a TA49 the exhaust housing needs to be machined out to fit a bigger wheel. The T31 turbine wheels like on the TA49 also have a different pitch. So they are all different wheels in the same housing.

 

[Nigel]

Good stuff, looking forward to reading future reports.

 

[turbo89]

I don't know... once I find the limit then there are probably a few things to test out to see if it makes any difference. And I'm on pump gas and alky too. Maybe try out E85 or different fuel. I think the turbo will be the limiting factor though.

And if I upgrade the turbo then the engine will probably become the limiting factor. Upgrading the cam and even a minimal port on the heads will probably make a big difference. It would be cool to see how far I can push a stock engine on a bigger turbo though and probably will be the next step down the road, but could be a while....

As far as your statement about the exhaust wheel being the limiting factor, not a turbo expert but that seems to be the case. From what I understand even though the same .63 Garrett Housing is used on other turbos all the turbine wheels are larger than the stock one. So even when you upgrade to a TA49 the exhaust housing needs to be machined out to fit a bigger wheel. The T31 turbine wheels like on the TA49 also have a different pitch. So they are all different wheels in the same housing.

Update the springs .. that will help

 

[TurboBob]

if the goal is to see how far the stock turbo can go, you can have the exhaust wheel clipped. And perhaps extrude-hone the exhaust housing.

Bob