GTP 38 Build Help Please.

[corum8488]

Hello, So has anyone here done a build with a GTP 38 turbo. I've used jetspecs to get all my numbers for the flame tube 2.36" diameter inducer, flame tube length=14.17" X Dia.=5", .25" Primary X27, .375" Secondary X8, .625" tertiary X7. I left a .75" gap between the flame tube and the outer can. The output side of the flame tube there is a cone that goes from 5" to 3.5 in V clamp. The air handler is 3 in tube, the bends are pie cuts. So here is my problem I have a good hot flame ample air flow and nothing, it doesn't even try to increase RPM. I've tried increasing fuel decreasing fuel I've added holes to all three zones systematically as well as removed holes. I've tried different fuels I've tried increasing the air flow. nothing I do seems to have any affect. I'm stumped and out of ideas. Did I miss something? This is my second build my first engine was a ebay special cheapo turbo and that one worked till I pushed it to hard and too hot and shattered the turbine blades. I would be grateful for any input.

[racket]

Hi

What fuel are you using and how is it injected ??

Is there a wastegate in the turb scroll??

What size turb scroll A/R ??

What sized turb wheel exducer ??

Cheers
John

[corum8488]

Im using propane 1st then switching to regular gasoline. There was a waste gate but i have it held shut by a large spring. The A/R is 1.0the exducer is 3.4 inches.
I also have a simple cone shaped nozzle that goes from 3.5 inches to 2.25 inches that clamps to the turbo but it had no noticeable effect.

[corum8488]

The fuel is injected via automotive fuel pump with a bypass at 100 psi through needle valve then a oil burner nozzle (70 deg. spray at 28GPH (@ 100 psi)). so between the bypass valve and the needle valve just before the nozzle I have a wide range of flow and pressure control. The propane is fed directly to a single port nozzle (no regulator) via a needle valve but it is just used to aid in the ignition of the gasoline. I have tried K-1 as well as waste oil with the same set up but again with no noticeable effect.

[racket]

Hi

Thanks for the extra info

Your fuel spray nozzle is way too big, probably resulting in very poor atomisation , it needs to be closer to 8 GPH rather than 28 GPH , I'd even go for a 5GPH nozzle to start with to get the engine fired up so you can sort things out .

Cheers
John

[corum8488]

ok got a 5GPH nozzle. Now I can hear the turbo slightly start to spool up but its no where near self sustaining and the cone that goes from the combustion chamber to the turbine gets way to hot. I double checked the size of the holes and number of holes as well as the flame tube diameter and length (according to Jet Specs). There is a 3/4in. gap around the circumference between the flame tube and the outer can. The flame tube runs the entire length of the outer can with no gap at either end. with the new nozzle I've tried adding holes as well as going with less holes on each of the 3 zones, with no success. I have not as of yet tried adjusting the length or the diameter of the flame tube or moving the air inlet tube more to the center and perpendicular to the flame tube. As these adjustments would take some time and i am unsure of which way to try; longer, shorter, larger diameter or smaller diameter. If someone could point me in the right direction, please.

[racket]

OK , if it sounds better then we're making progress :-)

Lets talk about starters................what are you using, how are you using it ??

Cheers
John

[corum8488]

I have 2 options for starting electric leaf blower and a SCUBA tank filled to 3000 PSI no regulator

[racket]

How are you using them ??

[corum8488]

With the leaf blower as well as the SCUBA tank I start on low to ignite then wait till the combustion chamber warms up then on hi when I switch fuels.

[racket]

Is the leafblower sealed against the comp housing , no leakage, when on high speed ??

How is the scuba air supplied to the engine , in what position ??

What rpm are you achieving with just the blower/scuba, no fuel ??.

[slittlewing]

corum8488 I think a video posted on youtube or similar would help to diagnose what the problem is.

[corum8488]

I got it running. I had an air leak around the rubber seal that I was using to connect the compressor output to air handler. I made the repair and went for start up the turbo spooled right up to full throttle at this moment I realized that I had forgotten to turn the oil pump on I shut it down as fast as possible but it was to late the bearings are cooked. I've ordered a rebuild kit. Once the repairs are made I will post the results of the next test. Thank you for all your help it is much appreciated, I'm positive I will need more input to fine tune the engine. Thanks again.

[smithy1]

May 8, 2021 19:09:07 GMT -5 corum8488 said:

I realized that I had forgotten to turn the oil pump on I shut it down as fast as possible but it was to late the bearings are cooked. 

An easy way to avoid this is to fit a "Hobbs" switch in the oil pump/fuel pump electrical circuit. This system won't let the fuel pump run unless there is oil pressure.... and when the engine is running, it shuts the fuel pump off if the oil pressure drops below the set point...which you can set to a safe desired pressure. It's a very simple solution to a potentially costly error.

Smithy.